On a pivot bolt which rotatably and pivotally supports a side stand bar on a vehicle-body-side bracket, a switch unit which is constituted of a base and a rotary made of a resin and detects a rotational position of the side stand bar is mounted. A first engaging mechanism which is constituted of a groove and a projection is arranged between a cylindrical portion formed on the rotary and an engaging shaft and, at the same time, a second engaging mechanism which is constituted of a groove and a projection is arranged between the base and the cylindrical portion. The rotary on which a movable contact formed of a leaf spring is mounted allows a positioning pin which is formed on one end portion thereof to be engaged with a pin hole formed in a pivot portion and hence, the rotary is integrally rotated with the side stand bar.