This three-dimensional surface roughness evaluating device is provided with a two-dimensional laser displacement meter, a movement mechanism which causes the two-dimensional laser displacement meter to move in the X-axis direction, a movement distance reading device which reads the movement distance of the two-dimensional laser displacement meter in the X-axis direction, and a calculating device which creates three-dimensional surface roughness data of a measured object on the basis of displacement data acquired by the two-dimensional laser displacement meter and movement distance data acquired by the movement distance reading device. The two-dimensional laser displacement meter is disposed in such a way that the width direction of the two-dimensional laser displacement meter coincides with the Y-axis direction, to make it possible to read Y-axis direction coordinate displacement data at fixed intervals. The measuring width of the two-dimensional laser displacement meter is at least twice a mean length RSm of
