This study points out the importance of the instruction about the communication strategy - i.e., task performance strategy and relation formation strategy- so that the learner can achieve the functions of the communication to perform a task and to form a relationship. Therefore, the experiment group was instructed about the communication strategy before cooperative learning method was applied to the group. The effect on the learning was evaluated and analyzed in comparison with the control group on the individual and group basis. The results showed significantly higher scores for the experiment group in terms of task function, relation function, learning attitude and language expression on the individual basis. And, also, on the group basis, the experiment group had significantly higher scores in terms of the cooperation, learning attitude, and learning outcome. These results imply that instruction about the communication strategy improves learner's capability to perform a task function and relation function and effects the learning attitudes and language expression. Besides, learning about the communication strategy improves cooperation among the group members, enables a sincere performance of the task and finally enhance the quality of the task performance and the outcome.