To provide an illumination device which draws strong interest of an observer and be useful for the traffic safety by attaching it to a rotating body such as a wheel of a bicycle.

This device is provided with a main body to be attached to a rotating body, an emitter element group 3 aligned in the main body, and a control means 20 for letting the emitter element group 3 emit by a preset standard. It is preferable that the emitter element group 3 is aligned by being directly attached to or embedded in the rotating body itself. This device is also provided with rotation angle detecting means (9, 25, 30) which detect the rotation angle of the rotating body and the controller 20 may control the emission of the emitter element group 3 according to the rotation angle detected by the rotation angle detecting means (9, 25, 30).