This paper analyses the influence of simultaneously offering non-audit services on audit quality(audit fee). We conducted empirical tests on how different types of auditors influence the relationship between simultaneously offering audit and non-audit services and audit quality by categorizing different types of auditor. Recent international trends focus on strengthening regulations against simultaneously providing non-audit services for fear of them hindering the independence of the auditor. While there are currently no country which specifically prohibits this, most countries only allow provision of non-audit services within a limited category in which there are very little cause for conflict of interests. A preceding research data puts forward contrasting results that assert that an audit quality is unaffected and the simultaneous provision of audit and non-audit services adversely affects an auditor’s independence and thus compromise the quality of the audit. Therefore, in contrast to previous studies, this paper conducted empirical tests on the influence of auditor’s provision of audit and non-audit services on the audit fee while also considering the type of auditor and the type of non-audit services offered. Furthermore, unlike most existing studies, this study separated between the types of auditor types depending on Big4, non-Big4 and the Financial Supervisory Service and also took into consideration one‐firmtype auditors’ characteristics in the empirical test. We also analyzed the influence of different types of non-audit services in the relationship between the simultaneous provision of audit and non-audit service and the audit fee. Non-audit services were divided into types such as tax service and non-tax services. We selected total 11,601 firm/years from 2002 to 2013 as the samples, targeting non-financial companies of December 31 fiscal year-end listed on the KOSPI and KOSDAQ of the 2013 year-end and have done an empirical analysis. The main results of this study’s empirical tests are as follows. First, simultaneous provision of audit and non-audit services has a significantly positive influence on the audit fee. Second, there is a difference in the level of influence exerted by the simultaneous provision of audit and non-audit services depending on the type of auditor. For example, Big4 and One firm showed significant and positive influence. While it also showed a significant positive influence of the Group1(GR1), Group2(GR2) showed no significant results. Division of Group1(GR1) into Big4 and DSS (herein referred to as Local Big3) did not result in any significant results for DSS. This is because the significance of Big4 largely influenced Group1(GR1) overall and in practice, despite DSS’s ability to acquire audits, DSS does not divide audit and non-audit divisions like the Big4 and One firm, there have been numerous cases where the same partner provided both audit and non-audit services. Third, according to analysis of each type of non-audit services in influencing the relationship between the provision of audit and non-audit services and the audit fee, there were differences between tax services and non-tax services. The current mandatory auditor designation system was introduced in January 1990 as a means to protect investors and ensure the independence of the auditor from the free audit engagement contracts. The system takes into considering the auditor’s special features and divides a number of auditors to the four groups. Then, the designated companies are allocated to the auditors. From December 2014, an amendment was passed for the relevant legislation requiring reasons for designations and this is forecasted to drastically increase the number of designated companies. As there are ongoing discussions on improving the appointment method, including through public hearings on February 2015, changes to the appointment method from categorizing auditors based on their quality assurances need to occur. In 2011, Financial Services Commission discussed improvement plans and basic auditor registration based on evaluation results and filling out an evaluation criteria to enhance and ensure the independence of the external auditor. Ultimately, securing transparent accounting and independence of auditors will help Korea step one step closer to becoming a transparent and fair society. As reinforcement of non-audit service related policies are being emphasized internationally, it appears to be the right time to differentiate different types of non-audit services, introduce quality assurance systems to improve independence of the auditor and study policy developments. It is hoped that the recently discussed mandatory auditor designation system improvement plans and new appointment criteria based on different types of audits and other measures to secure the independence of auditors become the most pressing directions.