A control method for a work machine, includes: detecting a posture of a working unit driven by a hydraulic cylinder in a movable range; determining whether the working unit at a stop position of the movable range has started moving based on an operation of the working unit; setting a deceleration section including an end position of the movable range and a deceleration ratio of the working unit in the deceleration section, based on the posture of the working unit in a stopped state at the stop position, and a threshold determined in advance; and outputting a command signal to a control valve, which is capable of adjusting an amount of a working oil supplied to the hydraulic cylinder, such that the working unit moves from the stop position to the end position based on the deceleration section and the deceleration ratio.