A brain-computer interface (BCI) reflects a user's intention using brain information as input and is expected to work as a communication support system to assist people who have disabilities such as paralysis. In the present study, we focus on brain activity in the prefrontal cortex. We measured the brain activity in the prefrontal cortex by near-infrared spectroscopy (NIRS) and electroencephalogram (EEG), and developed a BCI system.