In order to explain the consumer decision process in the fixed pricing group buying (FPGB) context, this study proposed an FPGB decision model from the social perspective. To reflect the social perspective, the proposed FPGB decision model included social factors such as network externalities and subjective norm as triggers for shopping motivations. According to the analysis results, all social factors directly or indirectly affected consumers' buying intention at FPGB websites. To be more specific, of the social factors, perceived complementarity was the most significant determinant of FPGB buying intention not just in the direct influential paths but in the indirect influential paths. Subjective norm did not directly affect FPGB buying intention, but it did indirectly. These results imply that the managers of FPGB websites should carefully consider social factors as triggers for shopping motivations when designing and operating FPGB websites.