The invention belongs to the field of precision and ultra-precision machining, and particularly relates to a near-field ultrasonic cavitation and fluid shearing combined type micro-gear finishing machining device and a machining method. The near-field ultrasonic cavitation and fluid shearing combined type micro-gear finishing machining device comprises a near-field ultrasonic cavitation system, afluid shearing system and a polishing solution circulation system, wherein the near-field ultrasonic cavitation system comprises an ultrasonic generator, a piezoelectric transducer, an amplitude-change rod, an upper supporting disc, a lower supporting disc and a precise support, the ultrasonic generator is connected with the piezoelectric transducer through a wire, the piezoelectric transducer isconnected with the amplitude-change rod through a double-head stud, a flange plate used for being fixed to the precise support is arranged on the amplitude-change rod, the amplitude-change rod is connected with the upper supporting disc through a bolt, the lower supporting disc is arranged below the upper supporting disc, a micro-gear is arranged on the lower supporting disc, and the micro-gear isconnected with a clamp through a bolt. According to the near-field ultrasonic cavitation and fluid shearing combined type micro-gear finishing machining device and the machining method, cavitation bubbles and solid abrasive particles of a polishing solution can effectively clean a micro-groove structure interface, so that efficient, precise, green and flexible finishing machining of the micro-gear is realized.