This study aimed to explore cognitive processing in language comprehension, focusing on how gaze direction influences the understanding of Japanese grammatical structures. Carlei & Kerzel showed that upwards gaze direction shortened reaction time significantly compared with lower gaze when a participant detects grammatical error in French language. In our experiment, the participant was presented with a series of Japanese sentences in the study. In each trial, the participants were instructed to direct their gaze toward one of the screen’s corners while determining the grammatical correctness of sentences. We provided 40 grammatically correct sentences and 40 sentences with grammatical errors. However, there were no significant main effects of gaze direction in Japanese language. These contradictory results suggested that phonological processing may be influenced by gaze direction. Web designers are recommended to place documents in the upper field of a display in European languages, while they do not need to pay any attention to visual fields in Japanese language.