This paper examines some aspects of previous contrastive studies of grammaticalization between Korean and Japanese. This study indicates some problems on the past studies and suggests how contrastive studies of grammaticalization between Korean and Japanese should be performed in the future. This study investigates the past contrastive studies of grammaticalization between Korean and Japanese through following sources: (i) the National Assembly Library in Korea and Japan, (ii) academic research information services such as RISS, DBpia, KISS, e-article in Korea, CiNii in Japan, Science Direct overseas, (iii) academic search engines such as Google Scholar and Yahoo, (iv) Japanese and Korean Linguistics vol.1-20. As a result, there exist 84 studies with 21 grammatical categories such as nominalizers, sentence-final markers, aspectual markers and adverbial particles. This paper suggests that future contrastive studies of grammaticalization between Korean and Japanese should be focused as followed: (i) a discrepancy in the degree of grammaticalization, (ii) a difference on the degrammaticalization of adverbial particles, and (iii) a study on language contact between Korea and Japanese.