To solve the problem that a steam cleaning apparatus for machinery parts, where it is known that the cleaning effect is remarkably improved, makes it impossible to obtain high torque in high temperature stream since steam is a gas and prevents a deceleration apparatus from being operated satisfactorily due to deformation such as thermal expansion because of high temperature steam if not only high-temperature steam jetting but also brushing is carried out.

A planetary deceleration manner using a two-step type taper rollers is employed and taper rollers having flanges are employed and to support a sun roll, no bearing is employed to simplify the structure. Contact plane pressure of rollers necessary for transmitting motive force is generated by force in the axial direction of a steam turbine or the pushing repulsive force acting on the rotary brush. The discharged gas of the steam turbine is led to the rotary brush part through the inside of a decelerator without bringing the gas into contact with the outside air and the steam at a saturation temperature is utilized for cleaning and the steam drain generated by heat release is simultaneously made usable for cleaning.