Provided are a cognitive function evaluation apparatus, a cognitive function evaluation method and system, and a program that can be implemented for non-handicapped persons and persons with severe motor impairment. The apparatus according to the present invention is an apparatus for evaluating cognitive function provided with a processing unit that analyzes and processes a brain wave caused by a plurality of stimulus events including a target and a non-target; estimates a stimulus event selected as the target from the plurality of stimulus events; determines a discrimination score or decoding accuracy; and evaluates cognitive function on the basis of a value of one or more of the discrimination score, the decoding accuracy, any of time courses, and decoding speed. With respect to two or more stimulus event groups having different levels of difficulty distinguishing between stimulus events, a discrimination score or decoding accuracy may be determined for each of the different difficulty levels, and cognitive function may be evaluated on the basis of a connection between one or more of the discrimination score, the decoding accuracy, any of time courses, and decoding speed and the difficulty levels.