A manipulator (21, 19, 12) comprising: a motor including a rotary shaft which rotates in accordance with a drive command signal; a reduction gear unit including a drive gear connected to the rotary shaft of the motor, and a plurality of gears including a gear that meshes with the drive gear; a detection unit which detects an operation state of the motor; a tube body having a movable body which is driven by the motor through the reduction gear unit; a load calculation section which performs operation processing on the drive command signal to be supplied to the motor and detected information by the detection unit, and calculates a load acting on the motor as an estimated value; and a notification unit which notifies a calculation result of the load calculation section, characterized in that the load calculation section includes an operation block which calculates a disturbance estimated value (da) which is an estimated value of a disturbance load (d) exerted on a motor shaft as the rotary shaft of the motor, the operation block comprising a first operation block that calculates with a design motor torque constant (Ktn) with respect to a motor torque command value (u) as input, a second operation block which performs an inverse operation to obtain a torque exerted on the rotary shaft of the motor from the number of revolutions of the motor, and a subtraction block that estimates and outputs the disturbance load (d) by subtracting the output of the first operation block from the output of the second operation block, a detection unit which detects a rotational position of the motor, the detection unit being an encoder that is connected to the rotary shaft of the motor, a position detection unit which detects a rotational position of the gear, the position detection unit being a potentiometer that is connected with a rotary shaft of the gear, and a position data generator which generates position data (Pd) which corresponds to information on mesh positions between the plurality of gears constituting the reduction gear unit upon input of an output value of the detection unit and an output value of the position detection unit, wherein the manipulator further comprises a storage unit which stores in advance correction information of a periodical characteristic associated to approximate a high correlation value between the disturbance estimated value (da) and the mesh position between the plurality of gears constituting the reduction gear unit, the load calculation section estimates an estimated value of load by using the correction information, and the storage unit includes a lookup table, the lookup table reducing influence of meshing backlashes between the plurality of gears constituting the reduction gear unit upon input of the disturbance estimated value (da) and the position data (Pd), and outputting a disturbance estimated value (db) as periodical correction information depending on the mesh positions between the plurality of gears. a motor including a rotary shaft which rotates in accordance with a drive command signal; a reduction gear unit including a drive gear connected to the rotary shaft of the motor, and a plurality of gears including a gear that meshes with the drive gear; a detection unit which detects an operation state of the motor; a tube body having a movable body which is driven by the motor through the reduction gear unit; a load calculation section which performs operation processing on the drive command signal to be supplied to the motor and detected information by the detection unit, and calculates a load acting on the motor as an estimated value; and a notification unit which notifies a calculation result of the load calculation section, an operation block which calculates a disturbance estimated value (da) which is an estimated value of a disturbance load (d) exerted on a motor shaft as the rotary shaft of the motor, the operation block comprising a first operation block that calculates with a design motor torque constant (Ktn) with respect to a motor torque command value (u) as input, a second operation block which performs an inverse operation to obtain a torque exerted on the rotary shaft of the motor from the number of revolutions of the motor, and a subtraction block that estimates and outputs the disturbance load (d) by subtracting the output of the first operation block from the output of the second operation block, a detection unit which detects a rotational position of the motor, the detection unit being an encoder that is connected to the rotary shaft of the motor, a position detection unit which detects a rotational position of the gear, the position detection unit being a potentiometer that is connected with a rotary shaft of the gear, and a position data generator which generates position data (Pd) which corresponds to information on mesh positions between the plurality of gears constituting the reduction gear unit upon input of an output value of the detection unit and an output value of the position detection unit, wherein