A work machine comprising: a hydraulic pump driven by a prime mover; a multijoint type front work implement configured such that a plurality of driven members including at least a boom, an arm, and a work tool are coupled rotatably; a plurality of hydraulic actuators (32, 34, 36) each driven by a pressurized fluid delivered from the hydraulic pump and driving each of the plurality of driven members; a plurality of directional control valves (43, 44) each controlling a direction and a flow rate of the pressurized fluid supplied from the hydraulic pump to each of the plurality of hydraulic actuators (32, 34, 36); a plurality of operation devices (51, 52) controlling the plurality of directional control valves (43, 44); a plurality of operation amount sensors (51a, 52a, 52b) detecting operation amounts of the operation devices (51, 52) related to at least the boom and the work tool among the plurality of operation devices (51, 52); and the work machine is characterized in further comprising: a flow restriction device (45; 46; 47a, 47b) that can restrict a flow rate of the pressurized fluid in at least one of a meter-in passage and a meter-out passage of one of the directional control valves (43, 44), the one directional control valve being related to the work tool; and a controller (60; 60A; 60B) controlling the flow restriction device (45; 46; 47a, 47b) on the basis of detection results of operation amounts from the plurality of operation amount sensors (51a, 52a, 52b), wherein the controller (60; 60A; 60B) is configured to be capable of changing over an action mode to any one of a normal mode for restricting a flow rate of the pressurized fluid by the flow restriction device (45; 46; 47a, 47b) and a responsiveness priority mode for not restricting the flow rate of the pressurized fluid by the flow restriction device (45; 46; 47a, 47b) in response to the detection results of the operation amounts of the plurality of operation devices (51, 52). a hydraulic pump driven by a prime mover; a multijoint type front work implement configured such that a plurality of driven members including at least a boom, an arm, and a work tool are coupled rotatably; a plurality of hydraulic actuators (32, 34, 36) each driven by a pressurized fluid delivered from the hydraulic pump and driving each of the plurality of driven members; a plurality of directional control valves (43, 44) each controlling a direction and a flow rate of the pressurized fluid supplied from the hydraulic pump to each of the plurality of hydraulic actuators (32, 34, 36); a plurality of operation devices (51, 52) controlling the plurality of directional control valves (43, 44); a plurality of operation amount sensors (51a, 52a, 52b) detecting operation amounts of the operation devices (51, 52) related to at least the boom and the work tool among the plurality of operation devices (51, 52); and the work machine is characterized in further comprising: a flow restriction device (45; 46; 47a, 47b) that can restrict a flow rate of the pressurized fluid in at least one of a meter-in passage and a meter-out passage of one of the directional control valves (43, 44), the one directional control valve being related to the work tool; and a controller (60; 60A; 60B) controlling the flow restriction device (45; 46; 47a, 47b) on the basis of detection results of operation amounts from the plurality of operation amount sensors (51a, 52a, 52b), wherein the controller (60; 60A; 60B) is configured to be capable of changing over an action mode to any one of a normal mode for restricting a flow rate of the pressurized fluid by the flow restriction device (45; 46; 47a, 47b) and a responsiveness priority mode for not restricting the flow rate of the pressurized fluid by the flow restriction device (45; 46; 47a, 47b) in response to the detection results of the operation amounts of the plurality of operation devices (51, 52). a flow restriction device (45; 46; 47a, 47b) that can restrict a flow rate of the pressurized fluid in at least one of a meter-in passage and a meter-out passage of one of the directional control valves (43, 44), the one directional control valve being related to the work tool; and a controller (60; 60A; 60B) controlling the flow restriction device (45; 46; 47a, 47b) on the basis of detection results of operation amounts from the plurality of operation amount sensors (51a, 52a, 52b), wherein the controller (60; 60A; 60B) is configured to be capable of changing over an action mode to any one of a normal mode for restricting a flow rate of the pressurized fluid by the flow restriction device (45; 46; 47a, 47b) and a responsiveness priority mode for not restricting the flow rate of the pressurized fluid by the flow restriction device (45; 46; 47a, 47b) in response to the detection results of the operation amounts of the plurality of operation devices (51, 52).