Using functional magnetic resonance imaging (fMRI), much knowledge has been gained in understanding how the brain is activated during controlled experiments of language tasks in alphabetic subjects and in logographic language subjects. While previous studies have compared performance between alphabetic and Chinese subjects, few data were about Japanese-speaking individuals. In this study, we used fMRI to investigate brain activations in processing Japanese semantic and font size judgment by visual tasks in six Japanese subjects. Different activation patterns were observed between semantic and font size judgment processing. We conclude that constellation of neural substrates was different for semantic processing.