In a reactor cleaning apparatus 1 which cleans an inner wall surface 72 of a reactor 70 which generates polycrystalline silicon, a bell jar of the reactor 70 has a dual structure, a through hole 11 is formed along a vertical direction at a central portion of a substantially disc-like tray 10 placed in a horizontal state, a flange portion 13 in which an opening edge of the reactor 70 is placed is formed at an outer peripheral portion of the tray 10, a shaft 20 is provided through the through hole 11 of the tray 10 so as to be rotatable and movable in the vertical direction, a nozzle device 50 which sprays a cleaning water at high pressure in three-dimensional directions is provided at an upper end of the shaft 20, a drive mechanism 30 which rotates the shaft 20 and moves the shaft in the vertical direction is provided at a base end of the shaft 20, and steam piping 62 capable of supplying the steam within the bell jar of the reactor 70 is provided.