The present research investigated activities in the prefrontal cortex while performing the Rorschach inkblot method (RIM) using functional near-infrared spectroscopy. Participants who had no history of mental illness or external head injury were presented with three International RIM Cards (I, IV, V) for 30 s each and asked to identify what they looked like. In addition, a picture task was conducted, in which simple pictures were used as visual stimuli and participants were asked to say what they were. Results showed significant increase of oxyhemoglobin over time with nearly all measurement channels on the RIM task. The volume changes in oxyhemoglobin during both the middle and late segments of the RIM task were more significant than those of the picture task in almost all channels with the exception of no significant difference in the middle with a few right lateral channels. With regard to deoxyhemoglobin, on the RIM task, a significant decrease was observed with nearly all channels, but only in some of the task segments. These results are then discussed in regards to the function of the prefrontal cortex.