To provide a cabin light configured to prevent a size increase of its body and to suppress strength reduction.

The cabin light includes a housing 20 having a light-emitting diode substrate 40 and a substrate mounting surface 21 on which the light-emitting diode substrate 40 is mounted, and a lens 30 which is made of a translucent resin and is attached to the housing 20 to cover the light-emitting diode substrate 40. The substrate mounting surface 21 is provided with positioning ribs 23 formed into a projecting shape corresponding to the outline of the light-emitting diode substrate 40. Each of the positioning ribs 23 has a fastener receiving hole 24 bored thereon, which receives a fastener for fixing the housing 20 in a vehicle.