This study investigates the factor that promotes technological breakthrough by the established firm, focusing on the individual behavior of inventors. Especially, I hypothesize the effect of “deviant behavior” of inventors on the radicalness of technologies invented by those inventors. Using patent data of Nippon Telegraph and Telephone Corporation, I show the effect of deviant behavior depends on the reference point of the newness of technologies. This study highlights the role of deviant inventors as a source of technological exploration for the focal firm, not technological breakthrough which has high impact to other firms.