A landing gear lifting/lowering Electro Hydrostatic Actuator system (10, 100), comprising: a hydraulic actuator (21, 22) configured to be attached to a leg of an aircraft and configured to lift and lower the leg; at least one electrically operated hydraulic pump, comprising at least one hydraulic pump driven by an electric motor, configured to supply a hydraulic fluid to the hydraulic actuator (21, 22) at a time of lifting or lowering the leg; a hydraulic path connecting the hydraulic actuator (21, 22) and the electrically operated hydraulic pump; a pressure sensor (38, 39) attached to the hydraulic actuator (21, 22) or the hydraulic path and configured to output a measurement signal corresponding to a hydraulic pressure; and a sensor configured to output a measurement signal corresponding to a revolution speed of the at least one hydraulic pump and/or the electric motor, and; a control unit configured to receive the measurement signals and characterized in that it is further configured to output to the electrically operated hydraulic pump, a control signal based on the hydraulic pressure and the revolution speed, wherein, when a state in which the revolution speed of the electrically operated hydraulic pump is not more than a set revolution speed and the hydraulic pressure exceeds a set pressure continues for a set time while the leg is being lifted, the control unit stops the electrically operated hydraulic pump in operation and resumes the operation of the electrically operated hydraulic pump after the hydraulic pressure drops to or below a second set pressure after the electrically operated hydraulic pump is stopped. a hydraulic actuator (21, 22) configured to be attached to a leg of an aircraft and configured to lift and lower the leg; at least one electrically operated hydraulic pump, comprising at least one hydraulic pump driven by an electric motor, configured to supply a hydraulic fluid to the hydraulic actuator (21, 22) at a time of lifting or lowering the leg; a hydraulic path connecting the hydraulic actuator (21, 22) and the electrically operated hydraulic pump; a pressure sensor (38, 39) attached to the hydraulic actuator (21, 22) or the hydraulic path and configured to output a measurement signal corresponding to a hydraulic pressure; and a sensor configured to output a measurement signal corresponding to a revolution speed of the at least one hydraulic pump and/or the electric motor, and; a control unit configured to receive the measurement signals and characterized in that it is further configured to output to the electrically operated hydraulic pump, a control signal based on the hydraulic pressure and the revolution speed, wherein, when a state in which the revolution speed of the electrically operated hydraulic pump is not more than a set revolution speed and the hydraulic pressure exceeds a set pressure continues for a set time while the leg is being lifted, the control unit stops the electrically operated hydraulic pump in operation and resumes the operation of the electrically operated hydraulic pump after the hydraulic pressure drops to or below a second set pressure after the electrically operated hydraulic pump is stopped.