To make surely detectable a carrying failure of recording material in a fixing device by conducting light inside from outside a fixing device frame member by a light guide and monitoring the carrying of the recording material in the fixing device from outside the frame member of the fixing device.

In this image forming device, a light emitting part 17 is provided facing an edge part 15b that is projected outside the frame member 1 of the light guide 15 and a light receiving part 18 is provided facing an edge part 16b projected outside the frame member 1 of the light guide 15. The light from the light emitting part 17 is guided horizontally by the light guide 15 as indicated by L in a diagram, guided horizontally by an edge part 16a of the light guide 16 after being guided vertically by an edge part 15a in the approximate center of the carrying path of the recording member and light is emitted from the edge part 16b of the guide 16 and received by a light receiving part 18. Here, when the recording material is detected to have passed the fixing device within a time corresponding to an image forming process, the recording material is discriminated to be carried normally.