Digital transformation is becoming a huge trend in the industry. However, successful cases of digital transformation promotion are rarely reported. Therefore, the need to explore various cases of digital transformation and analyze success and failure factors is raised. The purpose of this study is to conceptualize a digital transformation diffusion model based on innovation diffusion and chasm theory, and to verify the validity of the model through analysis of digital transformation promotion cases. The diffusion process of innovation takes the form of S-curve, and due to the discontinuity of innovation, the diffusion of innovation requires a considerable adjustment period. This is called chasm. Therefore, digital transformation can only succeed if chasm is overcome. The digital transformation diffusion model is a conceptualized model based on this theoretical background. In particular, we confirmed through the case of digital transformation promotion that the case companies are following the pattern suggested by the digital transformation diffusion model. This study is significant in that various types of digital barriers form chasm in the process of promoting digital transformation, and it presents a framework for analysis and alternative proposals.