A control unit is configured to calculate a target absorption torque of a hydraulic pump at which the engine output torque and the absorption torque of the hydraulic pump match a target matching rotation speed of the engine. The control unit is configured to refer to command data, calculate a command current value corresponding to the target absorption torque, and output a command signal of the calculated value to a pump control device. The control unit is configured to calculate the absorption torque at calibration points at which there is an equilibrium state in which the output horsepower of the engine and the absorption horsepower of the hydraulic pump are matched. The control unit is configured to acquire calibration information including the calculated absorption torque and the command current value output to the pump control device in the equilibrium state, and calibrate the command data based on the calibration information.