To provide a drum unit which is capable of making the number of parts smaller and simplifying structure by performing grounding of a Zener substrate and rotation stopping and coming-off stopping of a drum shaft by one part.

In the drum unit 1 which is configured in such a manner that a photoreceptive drum 3 rotating around a fixed drum shaft 6 and an electrifier 4 electrifying the photoreceptive drum 3 are integrally provided and the Zener substrate 13 for adjusting the potential of the grid of the electrifier 4 is disposed on one end side in the axial direction of the photoreceptive drum 3, an engaging groove 6a is formed at one end in the axial direction on a side where the Zener substrate 13 is disposed, of the drum shaft 6, while the ground contact of the Zener substrate 13 and the drum shaft 6 are conducted by a coil spring 17 and the free end 17c of the coil spring 17 is engaged with the engaging groove 6a formed in the drum shaft 6.