A control method controlling a work machine including a working unit with a working tool, comprising: obtaining a position of the working unit based on a detected position information item of the work machine and generating a target excavation ground shape information item indicating a target shape of an excavation target of the working unit from an information item of a design face indicating the target shape; and performing an excavation control of restraining the working unit from performing an excavation beyond the target shape based on the target excavation ground shape information item and, when the target excavation ground shape information item is not able to be acquired during the excavation control, continuing the excavation control by storing the target excavation ground shape information item obtained before a time point at which the target excavation ground shape information item is not able to be acquired, for a predetermined time.