Our study investigates the process of topic comprehension in comparative sentences and the relationship between this process and the word order of topic and vehicle. Our experiment used a meaningfulness decision task with three conditions: no-vehicle sentence (e.g. a word hurts someone), vehicle-after-topic sentence (e.g. a word, like a weapon, hurts someone), and vehicle-before-topic sentence (e.g. like a weapon, a word hurts someone.) The results of the meaningfulness decision task show that the vehicle-after-topic sentence and the vehicle-before-topic sentence were judged as meaningful more quickly than the no-vehicle sentence. Especially in comparative sentences with low conventional vehicle, the vehicle-before-topic sentences were judged more quickly than the vehicle-after-topic sentences.