The invention discloses an automatic tapping machine and relates to a processing device used for processing internal screw threads. The automatic tapping machine disclosed by the invention comprises a PLC (Programmable Logic Controller) control circuit, a machine base 051, a marble slab 052, an instrument lathe 053, a positioning adjustment device 054, a limiting device 055, a feed device 056, a tapping device 057, a clamping device 058 and a deceleration motor 059, wherein the marble slab is arranged on the machine base, the positioning adjustment device and the instrument lathe are fixed onthe marble slab, and the deceleration motor is arranged at one side of the instrument lathe. Being controlled by the PLC control circuit, the feed device quickly conveys workpieces, the limiting device ensures the workpieces to be accurately clamped, and the tapping device completes the accurate positioning of screw taps and is matched with the clamping device to complete the tapping process. Theinvention aims to provide the automatic tapping machine to solve the technical problem that manual intervention is needed in the processes of feeding, positioning, clamping, tapping and loosening, and through the invention, the processing speed and the processing accuracy are improved.