A work machine comprising: a diesel engine including an engine controller; at least one hydraulic pump driven by the diesel engine; at least one hydraulic actuator (10, 11) driven by hydraulic fluid delivered from the hydraulic pump, a revolution speed instruction unit for setting a target revolution speed of the diesel engine; and a machine controller for setting the target revolution speed of the diesel engine according to an instruction signal from the revolution speed instruction unit and outputting the set target revolution speed to the engine controller, characterized in that the engine controller is configured to provide a first revolution speed region including a rated revolution speed having a maximum output horsepower point and a second revolution speed region lower than the first revolution speed region and to control a fuel injection amount to limit a maximum output torque of the diesel engine in such a manner that the maximum output torque of the diesel engine in the second revolution speed region has a characteristic (Xa) of intermediate torque lower than a torque at the maximum output horsepower point in the first revolution speed region, wherein the machine controller is configured to output, to the engine controller, the target revolution speed set by the revolution speed instruction unit when the target revolution speed set by the revolution speed instruction unit is in the second revolution speed region and the hydraulic actuator (10, 11) is not driven, and calculate a required maximum output horsepower (He) at the target revolution speed set by the revolution speed instruction unit and increase the target revolution speed from a revolution speed in the second revolution speed region to a revolution speed in the first revolution speed region so as to obtain an output horsepower equal to the required maximum output horsepower (He) and output the increased target revolution speed to the engine controller when the target revolution speed set by the revolution speed instruction unit is in the second revolution speed region and the hydraulic actuator (10, 11) is driven. a diesel engine including an engine controller; at least one hydraulic pump driven by the diesel engine; at least one hydraulic actuator (10, 11) driven by hydraulic fluid delivered from the hydraulic pump, a revolution speed instruction unit for setting a target revolution speed of the diesel engine; and a machine controller for setting the target revolution speed of the diesel engine according to an instruction signal from the revolution speed instruction unit and outputting the set target revolution speed to the engine controller, characterized in that the engine controller is configured to provide a first revolution speed region including a rated revolution speed having a maximum output horsepower point and a second revolution speed region lower than the first revolution speed region and to control a fuel injection amount to limit a maximum output torque of the diesel engine in such a manner that the maximum output torque of the diesel engine in the second revolution speed region has a characteristic (Xa) of intermediate torque lower than a torque at the maximum output horsepower point in the first revolution speed region, wherein the machine controller is configured to output, to the engine controller, the target revolution speed set by the revolution speed instruction unit when the target revolution speed set by the revolution speed instruction unit is in the second revolution speed region and the hydraulic actuator (10, 11) is not driven, and calculate a required maximum output horsepower (He) at the target revolution speed set by the revolution speed instruction unit and increase the target revolution speed from a revolution speed in the second revolution speed region to a revolution speed in the first revolution speed region so as to obtain an output horsepower equal to the required maximum output horsepower (He) and output the increased target revolution speed to the engine controller when the target revolution speed set by the revolution speed instruction unit is in the second revolution speed region and the hydraulic actuator (10, 11) is driven.