A power generating apparatus of renewable energy type which generates power from a renewable energy source, comprising: a rotating shaft driven by the renewable energy source; a hydraulic pump driven by the rotating shaft; a hydraulic motor driven by pressurized oil supplied from the hydraulic pump; a generator coupled to the hydraulic motor; a high pressure oil line through which a discharge side of the hydraulic pump is in fluid communication with an intake side of the hydraulic motor; a low pressure oil line through which an intake side of the hydraulic pump is in fluid communication with a discharge side of the hydraulic motor; a motor target output determination unit which determines a target output of the hydraulic motor, POWER motor, based on a target output of the hydraulic pump, POWER pump; a motor demand determination unit which determines a displacement demand D m of the hydraulic motor; and a motor controller which adjusts displacement of the hydraulic motor to the determined displacement demand D m, characterised in that the motor demand determination unit obtains: a nominal motor demand D n of the hydraulic motor by dividing the target output of the hydraulic motor, POWER motor by a rotational speed of the hydraulic motor and an oil pressure P s in the high pressure oil line, a target oil pressure P d in the high pressure oil line based on the target output POWER motor, and a demand correction D b determined from a difference between the oil pressure Ps in the high pressure oil line and the target oil pressure P d, and the motor demand determination unit determines the displacement demand D m of the hydraulic motor from a sum of the nominal motor demand D n and the demand correction D b. a rotating shaft driven by the renewable energy source; a hydraulic pump driven by the rotating shaft; a hydraulic motor driven by pressurized oil supplied from the hydraulic pump; a generator coupled to the hydraulic motor; a high pressure oil line through which a discharge side of the hydraulic pump is in fluid communication with an intake side of the hydraulic motor; a low pressure oil line through which an intake side of the hydraulic pump is in fluid communication with a discharge side of the hydraulic motor; a motor target output determination unit which determines a target output of the hydraulic motor, POWER motor, based on a target output of the hydraulic pump, POWER pump; a motor demand determination unit which determines a displacement demand D m of the hydraulic motor; and a motor controller which adjusts displacement of the hydraulic motor to the determined displacement demand D m, characterised in that the motor demand determination unit obtains: a nominal motor demand D n of the hydraulic motor by dividing the target output of the hydraulic motor, POWER motor by a rotational speed of the hydraulic motor and an oil pressure P s in the high pressure oil line, a target oil pressure P d in the high pressure oil line based on the target output POWER motor, and a demand correction D b determined from a difference between the oil pressure Ps in the high pressure oil line and the target oil pressure P d, and a nominal motor demand D n of the hydraulic motor by dividing the target output of the hydraulic motor, POWER motor by a rotational speed of the hydraulic motor and an oil pressure P s in the high pressure oil line, a target oil pressure P d in the high pressure oil line based on the target output POWER motor, and a demand correction D b determined from a difference between the oil pressure Ps in the high pressure oil line and the target oil pressure P d, and the motor demand determination unit determines the displacement demand D m of the hydraulic motor from a sum of the nominal motor demand D n and the demand correction D b.