This research was designed to examine how the knowledge of kanji in their first language influences the processing of Japanese kanji-words for Korean learners. The participants were asked to read Japanese kanji-words, and the reaction time until they actually began to read was measured. Two experiments were conducted with learners of two different proficiency levels. The first involved kanji-words whose written forms are similar in the two languages. The second involved kanji-words which are similar phonologically. The following results were determined: (1) Highly proficient learners showed shorter reaction times than the less proficient learners, but the reaction times were not dependent on whether the written forms of stimulus kanji-words were similar to those in L1; (2) reading kanji-words which are similar phonologically required less time for learners of both levels. The results of this research differed slightly from an earlier experiment using singular kanji where the reading of those kanji characters whose written forms are similar was slower in the case of higher proficiency learners. In the current experiment, no difference in reaction time was observed between the two levels for similarity of form. It was suggested that for Korean learners, in reading Japanese kanji-words, unlike singular kanji characters, the exact form is of less importance, while concrete meaning and sound play a larger role.