A cognitive function evaluation device includes: an obtainment unit configured to obtain, as gait data, at least one of first data and second data, the first data indicating a sway amount of a body of a subject during walking in a first walking section from start of walking of the subject to a predetermined number of steps, and the second data indicating a sway amount of the body of the subject during walking in a second walking section in a double task state in which the subject is walking while doing a given assignment, the second walking section being after the first walking section; a calculation unit configured to calculate a feature value based on the gait data; an evaluation unit configured to evaluate a cognitive function of the subject, based on the feature value; and an output unit configured to output a result of evaluation by the evaluation unit.