An operation device includes three contact circuits each including fixed terminals and a slider as a movable contact for selectively changing a state between the fixed terminals to an ON/OFF state, a determination unit to which the contact circuits are connected, and an operation signal generation unit that outputs a signal indicating that an operation unit is in a state of ON operation. In response to an ON operation, the slider moves from an initial position where all contact circuits are in an OFF state to an end position where all contact circuits are turned on. Assuming that one of the contact circuits is a reference contact circuit and the others are output contact circuits, the reference contact circuit is provided such that a distance from the initial position to a position where the reference contact circuit is turned on is smaller than that for the output contact circuits.