This researchs aim is to investigate the effect of metaphor comprehension on the topic/vehicle accessibility to the metaphorical meaning. One simple experiment that consisted of a metaphor-priming task and a meaningfulness decision task showed that after metaphor comprehension, the vehicle strongly activates the metaphorical meaning when both the conventionality and aptness of the vehicle are high, and not when only either is high. This result suggests that both the above factors participate in the categorization process that decides and identifies the metaphorical meaning of the vehicle. On the other hand, it was shown that following metaphor comprehension, the topic does not similarly activate the metaphorical meaning when the conventionality and aptness of the vehicle are high; the metaphorical meaning of the topic is weak when that of the vehicle is strong. On the basis of these results, we discussed the process and role of the topic/vehicle in metaphor comprehension.