To provide a leash device for pet enabling easy and safe walking of a pet even at night, etc., by making a lighting part to be detachable from the device body, use of the light as a separate tool, and easy exchange of the light or the device in case of failure and suitably meeting the improvement of the light part and the device body.

The leash device 1 for pet is provided with an engaging member attached to the tip end of a leash 2 having a prescribed length and engageable with an engaging object attached to a pet, wherein the leash 2 is freely delivered from and wound on a reel built in the device body 1a. The device body 1a has an illumination tool 3 having a light-emitting diode 31 and detachably attached to the device body 1a. The device body 1a is provided with a strap 6 to be held by the owner or hooked on a hooking member. A light-reflecting member may be integrated in the leash 2.