The purpose of this study was to examine the process of preschoolers' detection of inconsistency. In the first experiment, what kind of text structure produced a good effect on performance to detect inconsistency, was examined. The results showed that the text structure easy to apply the contextual expectation produced high performance. It was suggested that difficulty to use the contextual expectation on text had some effect on performance to detect inconsistency. In the second experiment, the effect of awareness of contextual expectation was examined. The results showed that Expectation-Groups produced better performance and clearer explanation than Non-Expectation-Groups. It was suggested that awareness of contextual expectation improved the performance of detection of inconsistency. From these results, the hypothesis might be that during information processing, it was monitored whether information matches the contextual expectation or not.