Switch device

A switch device comprising:

• a circuit unit that forms an electric circuit that detects at least one of disconnection and a short circuit of a wiring connecting an external device and the switch device;
• two terminals connected to the electric circuit, and configured to be connected to the wiring;
• a contact mechanism that moves in a movable direction to switch on and off of a contact of the electric circuit;
• and
• a circuit board on which the circuit unit, the two terminals, and the contact mechanism are disposed,
• wherein the electric circuit comprises at least one resistive element,
• wherein the circuit unit and the contact mechanism are disposed on an identical surface side of the circuit board,
• wherein the movable direction of the contact mechanism is perpendicular to an upper surface of the circuit board, and
• wherein the resistive element and the contact mechanism are coplanar in a plane perpendicular to the movable direction of the contact mechanism within at least a part of a movable range of the contact mechanism.