The invention provides an automatic tapping device based on a torque sensor. The automatic tapping device based on the torque sensor comprises a lathe bed arranged on a base. A drill press spindle anda stepping motor are arranged on the lathe bed. An output shaft of the stepping motor is connected with the drill press spindle. A control system is further arranged between the drill press spindle and the stepping motor to achieve electrical connection. The lower end of the drill press spindle is in shaft connection with the upper end of the torque sensor. The lower end of the torque sensor is in shaft connection with a tap chuck. The control system comprises a single-chip microcomputer connected with the torque sensor. The single-chip microcomputer is connected with an upper computer and astepping motor driver. The stepping motor driver is powered on by a 12V power supply and connected with the stepping motor. The invention further discloses a tapping method of the automatic tapping device based on the torque sensor. By adoption of the automatic tapping device based on the torque sensor and the tapping method of the automatic tapping device, the problems that in the prior art, whensmall-diameter tapping is conducted, the tapping efficiency is low, and a screw tap is prone to breakage are solved.