PURPOSE: To provide an illuminating device which is designed to eliminate a need for fumbling in the dark and besides facilitate lighting ON and lighting OFF operation.

CONSTITUTION: An illuminating device 8 is designed to provide a body frame 10 with a fluorescent lamp 15, and the body frame 10 is mounted on an installation surface such that it is rotated between a position spaced away from the installation surface of the back of the back rest 5 of a seat 1 in a vehicle and a position making contact with the installation surface. A limit switch is arranged to the body frame 10 and operated owing to rotation when the body frame 10 is rotated between the spaced position and the contact position, and lights ON and OFF the fluorescent lamp 15.