Syntactic primacy hypothesis has been proposed for the relationship between syntactic processing and semantic processing. The hypothesis insist that syntactic processing precedes semantic processing. In order to investigate the relationship between syntactic and semantic processes, the present study examined the native speaker of Japanese with a reading aloud task as well as a correction task for Japanese sentences, while monitoring the cortical hemodynamic activities by functional Near-Infrared Spectroscopy (fNIRS). For the sentence stimuli, we prepared congruent sentences (CON, e.g., {yogore-o otoshimasu}, remove the dirt (acc)), semantically violated sentences (V-SEM, e.g., {ongaku-o nimasu}, boil the music (acc)), and syntactically violated sentences (V-SYN, e.g., {chimu-ga kumimasu}, the team(nom) forms). The results showed the cortical activation in the regions responsible for syntactic and semantic processing during the V-SEM condition, while only the regions corresponding with syntactic processing was activated during the V-SYN condition. The results indicate that the syntactic processing is necessarily before semantic processing in Japanese.