To provide a water channel cleaning device allowing a worker to clean the inside of a water channel inexpensively without stopping the operation of a power station.

This water channel cleaning device has a mechanism provided with: a propulsion member 30 receiving water pressure of the water flowing in the water channel 1; a supporting frame 20 connected with the upstream side of the propulsion member 30; and cleaning members on the upstream side and the downstream side 21, 22 attached to an outer peripheral side of the supporting frame 20 and allowing the supporting frame 20 to spread toward the outer peripheral side in such a way that the cleaning members on the upstream side and the downstream side 21, 22 come into contact with an internal wall of the water channel 1.