This study investigated learners` prototypes of Japanese verbs, and examined what creates them. Three verbs tutaeru, nageru, and wasureru with different correspondence relationships between L1 and L2 meanings were considered. Prototypes were surveyed using production and judgment tasks; three levels of Korean Japanese learners completed the tasks, with native speakers of Korean and Japanese answering the same content in their own languages. Three factors of forming learners` prototypes were considered: concreteness of meaning, frequency of L1 and L2 use, and similarity of meanings. Results revealed that lower level learners have concrete meaning as a prototype of L1 or L2 has concrete meaning. Learners considered L1`s concrete meaning as a prototype even though L2 did not possess that meaning. L2`s concrete meaning displayed high prototypicality despite L1 not retaining that meaning. On the other hand, higher level learners tended to have a high frequency of using meaning as a prototype. From these results, the requirements of negative evidences and natural input circumstances were considered.