The spatial-verbal dichotomy of working memory tasks was investigated using event-related potentials. Using an n-back task with three levels of n (0-, 1-, and 2-back), participants either matched words presented at a fixed screen position (verbal task) or matched the locations of non-word symbols presented at various positions across the screen (spatial task). Therefore, these two conditions were separated without confound of location and stimulus. Factors of match and task loading (Stimulus and N-Back effect) were found significant in P2a, N2 and P3, whereas domain-specific lateralization (Hemisphere x Task interaction, the feature of perception) was found significant in EPC, P2a and N2 but not in P3. These results hint time course of match (before P2a beginning, 200 ms) and perception (before P3 beginning, 300 ms).