Method for manufacturing mirror device

A method for manufacturing a mirror device comprising a structure including a base portion and a movable portion supported on the base portion, and a mirror layer provided to the movable portion, the method comprising:

• a first step of preparing a wafer having a support layer, a device layer, and an intermediate layer disposed between the support layer and the device layer;
• a second step of forming a slit in the wafer such that the movable portion becomes movable with respect to the base portion by removing a part of each of the support layer, the device layer, and the intermediate layer from the wafer and forming a plurality of parts each corresponding to the structure in the wafer, after the first step;
• a third step of performing wet cleaning for cleaning the wafer using a cleaning liquid after the second step, wherein the wet cleaning is performed in a state where the movable portion is movable with respect to the base portion;
• and
• a fourth step of cutting out each of the plurality of parts from the wafer after the third step,
• wherein in the second step, a part of the intermediate layer is removed from the wafer by anisotropic etching.