The purpose of this research was to examine exploratively　the process of social contagion and other factors affecting achievement motivation of young adult workers in the workplace, focusing on “self-fulfillment achievement motive” and “competitive achievement motive”. An interview investigation was undertaken with 8 adults working for companies, and also a multi-stage path model was proposed, analyzing the questionnaire responses of 355 people.(1) “inference of self-fulfillment achievement motive of a colleague” had a direct impact on “change in self-fulfillment achievement motive”, and “inference of competitive achievement motive of a colleague” had a direct impact on “change in competitive achievement motive”; (2) Through a “recognition of reference power of a colleague”and “reaction to achievement motive of a colleague”, “inference of achievement motive of a colleague” had an indirect impact on “change in achievement motive”; (3) “inference of self-fulfillment achievement motive of a colleague” had a positive impact indirectly on “change in two aspects of motive”, and “inference of competitive achievement motive of a colleague” had a negative impact indirectly on “change in two aspects of motive”.