EXPOSURE DEVICE AND IMAGE FORMING DEVICE

PROBLEM TO BE SOLVED: To provide an exposure device capable of highly accurately exposing by reducing the distortion when the device is attached to an image forming device, and to attach the device to the image forming device with simple constitution and work. SOLUTION: As for the exposure device which is installed in the image forming device and for irradiating a photoreceptor with light based on image information, the device is provided with an optical system means 33 for emitting the light beam to the photoreceptor, and a case 32 for storing the optical system means, and fitting members 34 and 35 are arranged at three positions equivalent to respective apexes of a triangle on the peripheral part of the case, and two fitting members among three fitting members are attached to the device main body 11 of the image forming device by a fixing member, and one is supported freely with reference to the device main body, and the freely supported fitting member among the three fitting members arranged in the case is positioned on the optical axis of the light emitted from the optical system means.