This study aimed to investigate how Japanese children learn the accusative marker focusing on the question whether or not this learning process is verb-specific. Speech of two children talking with their caretakers from CHILDES corpus was analyzed. For each speaker, the frequency of each verb that appeared in the speech was calculated. Verbs that were used 1-3 times were considered as unproductive while those used 4 times or more as productive. The results showed that children's productive verbs were found to be productive in their caretakers' speech as well, suggesting an input-based statistical learning of verb for children. Furthermore, children used wo for both productive and unproductive verbs, supporting that the learning of accusative markers is a verb-specific process even in a low input circumstance, since the verb-specific learning is that the productive usage and non-productive usage are exist together.