There is provided an optical sensor that includes a base portion, an action portion, a reflecting member disposed at one of the base portion and the action portion, and a detection unit including a light source and a light receiving element disposed at the other one of the base portion and the action portion. In the optical sensor, a space between the detection unit and the reflecting member is filled with a light transmissive material, and a force and/or acceleration is detected due to the light receiving element detecting light emitted from the light source and reflected by the reflecting member.