fig1 shows the structure of the posture control means 40 according to the present invention a circular fixing member 41 with a hollow inside is fixed to the periphery of the cavity 1a the fixing member 41 in section is rectangular refer to fig1 inside the member 41 there are provided a number of metal balls 42 such as used in the pin ball game these metal balls 42 roll freely inside the hollow cavity of the circular fixing member 41 when the cleaning apparatus is at a level position the metal balls 42 are substantially evenly distributed when the cleaning apparatus is positioned inclined such as on a slope the metal balls 42 will roll over to one side as shown in fig1 thus shifting the center of gravity of the cleaning apparatus this saves energy and eliminates use of a great driving force to control the movement of the cleaning apparatus the posture of the cleaning apparatus can thus be easily shifted at a speed with less power the posture control of this type which helps reduction of the force required to drive the main body bears a great significance in a cleaning apparatus such as the present invention as it is manipulated and operated under water where there is almost no gravity although the metal balls 42 are employed in the embodiment mercury may be sealed instead in the fixing member 41 if.