An aperture switching device is described that includes a base, a casing fitted to cover the base, and clamping parts fixed to the base. The clamping parts are driving power source input terminals and a shape memory alloy wire with two ends electrically connects the clamping parts. The base has a first light transmission hole, a rotary connecting part, a sliding groove, and a position regulating part. The casing has a second light transmission hole that corresponds to the first light transmission hole. A movable bump is connected to the shape memory alloy wire and slidably disposed within the sliding groove. An elastic member is disposed between the position regulating part and the movable bump. An optical aperture switching unit is positioned with one end portion mounted on the rotary connecting part and the end portion includes a switching slot mounted on the movable bump.