PURPOSE: To enable the control of a variable pitch propeller without generating any cavitation noise by providing a memory in which non-cavitation generation area is memorized beforehand.

CONSTITUTION: When a desired ship speed condition is given to a control section 8 through an input means 9, the control section 8 determines the angle of blades and the revolutions corresponding to the speed conditions from a non-cavitation generation area stored in a memory means 10. When the angle of blades is determined to be a specified value within the range, in response to the above, the revolutions are determined within the same range. The angle of blades and the revolutions thus obtained by the control section 8 are given to a blade angle adjusting mechanism 7 and a rotation driving source 5 as control signals to obtain the angle of blades and the revolutions as desired.