The monitoring of the cortex during cognitive functions is being investigated by many different disciplines. Recently, functional near-infrared spectroscopy (fNIRS) has been extensively used to study hemodynamic changes in the Prefrontal Cortex (PFC) during cognitive testing, depending on the development of the technology. In this way, various pathologies belonging to the cortex and the limits of healthy activation were evaluated, group differences were investigated and new medical evidences were obtained to be used in clinics.. In the study, a new fNIRS system was designed and a measurement was taken during the Wisconsin Card Sorting Test (WCST) from 12 healthy participants. Areas of the prefrontal cortex were compared based on the hemodynamic change during the active test and it has been shown that the dorsalateral prefrontal cortex(DLPFC) have more activation than the other areas. The result is consistent with other WCST tests in the literature.