A case including a holding portion and a rotary part is used to fix a drawer device. A first sidewall of the drawer device has a first hole. The holding portion has a second sidewall and the drawer device is disposed in the holding portion. A second hole is located in the second sidewall. The position of the second hole is corresponding to the first hole. The rotary part is pivoted on an outer side of the holding portion through a first hinge portion and the first hinge portion is located between a first protrusion portion and a second protrusion portion. When the drawer device comes into the holding portion, the drawer device is in contact with the first protrusion portion, which makes the rotary part turn in a first rotating direction and the second protrusion portion pass through the second hole to be fixed in the first hole.