An electric tool system , comprising: an electric tool including a tightening unit configured to tighten a workpiece onto an attaching target by driving force of a motor , and a controller configured to control the tightening unit so as to adjust an output torque to be output from an output shaft of the tightening unit , and an inspection device including a measuring unit configured to measure a tightening torque value applied from the tightening unit , the inspection device being configured to, when a measured value of the tightening torque value measured by the measuring unit reaches a prescribed target value under inspection of the electric tool , transmit, to the electric tool , a calibration instruction signal representing a measured value of a tightening torque value currently applied, the electric tool further including a calibration processor (F8) configured to calibrate the controller in accordance with the measured value measured by the measuring unit of the inspection device , the calibration processor (F8) being configured to calibrate, based on the tightening torque value included in the calibration instruction signal, the output torque estimated by the torque estimation unit such that the magnitude of the output torque thus estimated approximates the tightening torque value represented by the calibration instruction signal, the electric tool system characterised in the controller including a torque estimation unit configured to estimate the output torque output from the output shaft with reference to a rotational speed and a change in a rotation amount of the motor , and in the controller being configured to stop rotation of the motor when the output torque estimated by the torque estimation unit reaches a torque set value. an electric tool including a tightening unit configured to tighten a workpiece onto an attaching target by driving force of a motor , and a controller configured to control the tightening unit so as to adjust an output torque to be output from an output shaft of the tightening unit , and a tightening unit configured to tighten a workpiece onto an attaching target by driving force of a motor , and a controller configured to control the tightening unit so as to adjust an output torque to be output from an output shaft of the tightening unit , and an inspection device including a measuring unit configured to measure a tightening torque value applied from the tightening unit , the inspection device being configured to, when a measured value of the tightening torque value measured by the measuring unit reaches a prescribed target value under inspection of the electric tool , transmit, to the electric tool , a calibration instruction signal representing a measured value of a tightening torque value currently applied, the electric tool further including a calibration processor (F8) configured to calibrate the controller in accordance with the measured value measured by the measuring unit of the inspection device , the calibration processor (F8) being configured to calibrate, based on the tightening torque value included in the calibration instruction signal, the output torque estimated by the torque estimation unit such that the magnitude of the output torque thus estimated approximates the tightening torque value represented by the calibration instruction signal, the electric tool system characterised in the controller including a torque estimation unit configured to estimate the output torque output from the output shaft with reference to a rotational speed and a change in a rotation amount of the motor , and in the controller being configured to stop rotation of the motor when the output torque estimated by the torque estimation unit reaches a torque set value. <EOS>