An accumulator is provided in an oil circuit of the pressure supply device and has a gas chamber for storing the pressure generated by the oil pump. A gas pressure judgment unit judges a soundness on the gas pressure of the gas chamber of the accumulator. A pitch movement judgment unit judges whether the pitch movement is performed soundly by the oil pressure accumulated in the accumulator if the gas pressure judgment unit judges that the gas pressure is sound. A start judgment unit judges a start condition to start the gas pressure judgment unit every predetermined period or when a start switch is operated.