Provided is a fog light unit of a vehicle that facilitates attachment and detachment of a light section attached to the vehicle body and is excellent in operability of the portable light. A fog light unit includes a base fixed to a body of the saddle vehicle and a light section that is detachable from the base. The light section has a built-in battery. The base and the light section are connected with a slide mechanism including a guide rail and an engaging portion that slides along the guide rail for engagement. The fog light unit further includes a lock mechanism configured to prohibit a slide motion of the slide mechanism, and the lock mechanism includes a lock pin that protrudes and retracts, and an engagement hole, with which the lock pin engages.