A work machine comprising: a hydraulic pump driven by a prime mover; a hydraulic actuator (23, 24) driven by a hydraulic fluid supplied from the hydraulic pump; a center bypass line having one side that is connected to a delivery side of the hydraulic pump, and another side that is connected to a hydraulic working fluid tank; an open-center directional control valve (25, 26) that is arranged on the center bypass line, and controls a flow of the hydraulic fluid to be supplied from the hydraulic pump to the hydraulic actuator (23, 24); a center bypass cut valve that is arranged on the center bypass line and between the directional control valve (25, 26) and the hydraulic working fluid tank; and a controller that controls an opening of the center bypass cut valve, characterized in that the controller is configured to restrict the opening of the center bypass cut valve if operation on the hydraulic actuator (23, 24) is in a fine operation state in which the operation on the hydraulic actuator (23, 24) is within a predetermined range representing a region of fine operation, and the fine operation state is continued longer than a predetermined period, and fully open the center bypass cut valve if operation on the hydraulic actuator (23, 24) is the fine operation state in which the operation on the hydraulic actuator is within the predetermined range representing the region of the fine operation, and a duration of the fine operation state is less than or equal to the predetermined period. a hydraulic pump driven by a prime mover; a hydraulic actuator (23, 24) driven by a hydraulic fluid supplied from the hydraulic pump; a center bypass line having one side that is connected to a delivery side of the hydraulic pump, and another side that is connected to a hydraulic working fluid tank; an open-center directional control valve (25, 26) that is arranged on the center bypass line, and controls a flow of the hydraulic fluid to be supplied from the hydraulic pump to the hydraulic actuator (23, 24); a center bypass cut valve that is arranged on the center bypass line and between the directional control valve (25, 26) and the hydraulic working fluid tank; and a controller that controls an opening of the center bypass cut valve, characterized in that the controller is configured to restrict the opening of the center bypass cut valve if operation on the hydraulic actuator (23, 24) is in a fine operation state in which the operation on the hydraulic actuator (23, 24) is within a predetermined range representing a region of fine operation, and the fine operation state is continued longer than a predetermined period, and fully open the center bypass cut valve if operation on the hydraulic actuator (23, 24) is the fine operation state in which the operation on the hydraulic actuator is within the predetermined range representing the region of the fine operation, and a duration of the fine operation state is less than or equal to the predetermined period. restrict the opening of the center bypass cut valve if operation on the hydraulic actuator (23, 24) is in a fine operation state in which the operation on the hydraulic actuator (23, 24) is within a predetermined range representing a region of fine operation, and the fine operation state is continued longer than a predetermined period, and fully open the center bypass cut valve if operation on the hydraulic actuator (23, 24) is the fine operation state in which the operation on the hydraulic actuator is within the predetermined range representing the region of the fine operation, and a duration of the fine operation state is less than or equal to the predetermined period.