The monitor device in the disclosure includes a base element furnished with a first face and a second face, a first member, a switch, a second member, and a link member. The first member is disposed on a side of the first face of the base element, enabled to approach toward and separate from the first face. The switch detects whether the first member has approached toward the first face up to a first distance therefrom. The second member is disposed on a side of the second face of the base element, enabled to approach toward and separate from the second face. The link member is connected to the first member such as to cause the first member to approach the first face up to the first distance therefrom, in association with the second member approaching the second face up to a second distance therefrom.