It is possible to perform three-dimensional shape measurement with easy processing, regardless of whether an object is moving or not. An image capturing unit (103) captures a captured image (I) including both a real image (I2) of the object (113R) and a mirror (101). A light amount changing unit (63a) changes a light amount of a virtual image (I1). An image separating unit (captured image separating unit 104) specifies, as a virtual image (Ib1), an image in a region having a different light amount (R1), in a captured image (Ia) in which the light amount is changed and a captured image (Ib) in which the light amount is not changed, and specifies an image in a region having the same light amount (R2) as a real image (Ib2). A three dimensional shape is reconstructed from the real image and so on that are specified.