A windmill pitch control device (1, 2) that includes an electricity accumulator capable of applying electricity to an electric motor coupled to a pitch drive device for changing a pitch angle of a blade of a windmill that is provided rotatably on a main shaft portion of the windmill, and that is able to control the pitch angle of the blade with the electricity of the electricity accumulator such that the pitch angle is changed in a direction in which a wind pressure exerted on the blade is reduced, the windmill pitch control device (1, 2) comprising: a motor controller configured to control storage and discharge of the electricity in and from the electricity accumulator, and to control the electric motor based on a control signal for pitch control for changing the pitch angle of the blade from a pitch controller that transmits the control signal; a battery remaining power detector configured to detect a battery remaining power of the electricity accumulator; and a pitch angle detector configured to detect the pitch angle of the blade; wherein the motor controller is connected to a main power source that is a power source for supplying electricity during normal operation such that the electricity is supplied to the motor controller, and at the time of a loss of an electricity supply capability of the main power source, the motor controller controls the electric motor with the electricity supplied from the electricity accumulator and continues the pitch control, based on the control signal, and controls for changing the pitch angle of the blade so as to perform a feathering control, when the remaining power detected by the battery remaining power detector is smaller than or equal to a predetermined value while the pitch control being continuously performed with the electricity supplied from the electricity accumulator; characterised in that, if the remaining power detected by the battery remaining power detector becomes smaller than or equal to a predetermined lower limit which is further smaller than the predetermined value, while the pitch control is being continued with the electricity from the electricity accumulator, the feathering control is performed with a direct power source which is different from the main power source and is connected to the electric motor; and wherein the feathering control is stopped at a predetermined position based on the result of detection by the pitch angle detector to complete the feathering control operation. a motor controller configured to control storage and discharge of the electricity in and from the electricity accumulator, and to control the electric motor based on a control signal for pitch control for changing the pitch angle of the blade from a pitch controller that transmits the control signal; a battery remaining power detector configured to detect a battery remaining power of the electricity accumulator; and a pitch angle detector configured to detect the pitch angle of the blade; wherein the motor controller is connected to a main power source that is a power source for supplying electricity during normal operation such that the electricity is supplied to the motor controller, and at the time of a loss of an electricity supply capability of the main power source, the motor controller controls the electric motor with the electricity supplied from the electricity accumulator and continues the pitch control, based on the control signal, and controls for changing the pitch angle of the blade so as to perform a feathering control, when the remaining power detected by the battery remaining power detector is smaller than or equal to a predetermined value while the pitch control being continuously performed with the electricity supplied from the electricity accumulator; characterised in that, if the remaining power detected by the battery remaining power detector becomes smaller than or equal to a predetermined lower limit which is further smaller than the predetermined value, while the pitch control is being continued with the electricity from the electricity accumulator, the feathering control is performed with a direct power source which is different from the main power source and is connected to the electric motor; and wherein the feathering control is stopped at a predetermined position based on the result of detection by the pitch angle detector to complete the feathering control operation.