A numeral quantifier in Japanese consists of a numeral and a classifier that agrees with the type of entity being counted. In this study we investigated, using event-related potentials, brain activities associated with the integration of a numeral classifier and a noun that denotes an entity⁄entities being counted. Based on previous studies, we considered two hypotheses. If semantic processes are crucially involved in the integration of a noun and a numeral classifier, like selectional restriction between a verb and its object, N400 would be found when subjects read incorrect pairs of a noun and a numeral classifier. On the other hand, if the integration of a noun and a numeral classifier is morpho-syntactic in nature, parallel to gender agreement in European languages, then LAN would be elicited. Results of our experiment showed that mismatch of a noun and a numeral classifier evoked N400. This suggests that a numeral classifier in Japanese semantically selects a noun denoting a certain type of entity.