This study was based on Elaboration Likelihood Model (ELM), which is a general theory of attitude change, and investigated effects of motivation and ability to process information on issue-relevant elaboration and attitude change. It employed need for cognition, which is a disposition about engaging in and enjoying effortful analytic activity, as a motivation factor and distraction during presentation of message as an ability factor. The result of elaboration confirmed the postulate on variation in elaboration proposed by the ELM the extent of elaboration became high when motivation and ability were relatively high, and the extent of elaboration became low when motivation and/or ability were relatively low. On the other hand, the result of attitude change didn't correspond with previous studies based on the ELM; not only subjects in relatively high elaboration (HM·HA high motivation-high ability condition) but also subjects in relatively low elaboration (LM·LA and HM·LA) changed their attitude by argument quality, especially through the strong message. Furthermore, the path analyses revealed that elaboration had an important role as a mediator between attitude and motivation or ability; they didn'taffect attitude directly but could affect it through the medium of elaboration.