Regional cerebral activity related to attention may be more useful as an evaluation index for attention levels than conventional task performance score-based methods. We therefore researched whether the quantitative evaluation of attention using regional cerebral activity, measured using near-infrared spectroscopy (NIRS), was appropriate. NIRS signals during the continuous performance test (CPT), which is well known as an attention test, were measured and analyzed. We confirmed activities in the regions that may be associated with the right-side anterior cingulate cortex (ACC), and on the estimated dorsolateral prefrontal cortex (DLPFC). Furthermore, there was a high correlation between activity on the DLPFC related to executive function and the performance score. Our study using cerebral activity could not quantify attention, but it opened the possibility of quantifying levels of executive function.