To reduce the cost by miniaturizing a splash guard and at the same time to improve a mud water intrusion preventing performance.

This disk device is provided with a drum-in disk 3 having a drum 31, a disk 32a, and a rotor part 32b, also provided with an outer rotor 32e, an inner rotor 32c, and a rotor bench part 32d in the rotor part 32b, and provided with the splash guard 9 covering the vehicle center side of the drum-in disk 3 including an opening part 33e of a storage chamber 33. The inner rotor 32c is formed continuous to the disk 32a, the rotor bench part 32d is disposed in the side of the vehicle outside of the disk 32a, and the splash guard 9 is formed in such a dimension that its outer circumference part is disposed in the inside diameter side of the rotor part 32b.