The life of modern society is going to be more scientific and rationalized. According to these trends, our dietary life was also dramatically changed. Family restaurants grew up by 30% every year was became the place of meeting and relaxation from the place of selling and eating. These demands request to improve an atmosphere, a facility and a service in family restaurants. The objective of the present study is to investigate the effect of the gap of service in family restaurant on customer loyalty based on Oliver's gap theory. These results could be contributed to make the strategy of marketing in family restaurants. The purpose of this study in detail is as below. First, it is determined the difference of its expectation and its outcome regarding on the family restaurant service. Second, it is investigated the relationship of the gap of family restaurant with customer satisfaction. The suggestions of the present study are as below. First, it is necessary to get a novel CI strategy to clean the environment of restaurant and to induce the customer desires for young females as a dominant customers. Second, it is need to improve the interior of restaurant and to develop foods for optimal dietary environments. Third, based on the customer loyalty of the present study, customer satisfaction belongs to optimal dietary environment and utilization, whereas the negative gap of service is commercial dietary goods and employee's service. Therefore, the continuous loyalty along with personal satisfaction intends to improve the maximized atmosphere and utilization on use. The main strategy of marketing could be focused on the improvement of commercial dietary goods and utilization for the satisfaction and demands of customers.