Machining unit with automatic tool changing function

The utility model relates to the field of automatic machining, and particularly discloses a machining unit with an automatic tool changing function. The machining unit with the automatic tool changing function comprises a rotating main shaft and an automatic tool changing module. The automatic tool changing module comprises a tool clamping assembly, a tool changing operation assembly and a middle transmission rod. The cutter clamping assembly comprises a mandrel and a plurality of external expansion pieces, and each external expansion piece comprises a locking arm; the tool changing operation assembly drives the mandrel to move axially. An operation hole which is formed in the rotating main shaft in a penetrating mode in the axial direction is formed in the rotating main shaft, one end of the operation hole corresponds to the tool clamping assembly, and the other end of the operation hole corresponds to the tool changing operation assembly. The machining unit can better adapt to rapid conversion among multipl