To improve the general versatility, the production efficiency and the like of an expansion device.

The expansion device is provided with an equipment body part and a pair of mounted parts extruded from the both ends of the equipment body part in a same direction. An elastic deformation part which can be elastically deformed in a direction away from a mounting face of an electronic equipment body and with which the expansion device is pressed to the mounting face with the expansion device mounted on the electronic equipment body is provided on at least one of the mounted parts of the expansion device. The expansion device is mounted on the electronic equipment body in such a manner that the pair of the mounting faces get caught in the pair of the mounted parts of the expansion device from both sides.