A control device for automatically controlling a pitch angle of a blade includes a hydraulic oil amount calculation unit and an open ratio setting unit. The hydraulic oil amount calculation unit is configured to calculate an amount of hydraulic oil passing through a blade tilt cylinder valve. The open ratio setting unit is configured to cause the blade tilt cylinder valve to open at a predetermined open ratio when a request for the pitch angle to be changed has been received, to cause the blade tilt cylinder valve to close when the calculated amount of hydraulic oil has reached a predetermined amount of hydraulic oil required for the change of the tilt angle, and to cause the open ratio to be smaller than the predetermined open ratio while a request for a predetermined action necessitating that hydraulic oil be supplied from a main valve is being received.