An engine starting/stopping switch device is provided that includes a switch unit that switches over switching modes in response to linear movement of a movable member, a push button that is linked to the movable member so as to drive the movable member in response to a pushing operation, and a coil antenna that outputs transponder drive radio waves for generating an electromotive force in a transponder built into a portable device, wherein the coil antenna (15) is disposed coaxially with the push button (14) so that at least part of the coil antenna (15) is inserted into the interior of the push button (14). This enables the operability of a push button to be improved and enables the size in the radial direction of the push button to be reduced.