The invention provides a piezoelectric ultrasonic salt-bath heating nitriding device, which comprises a shell provided with a heat insulation layer, a salt bath tank in the shell, a heating plate, a wiring support column and a top cover, and is characterized in that: two sets of piezoelectric ultrasonic devices are symmetrically arranged on the shell; each one of the piezoelectric ultrasonic device comprises an energy-collecting rod, an oscillating plate, an amplitude transformer, an energy transducer and a cooling box; the oscillating plate and the energy-collecting rod form an integral part; the oscillating plate is arranged in the salt bath tank and is connected with the amplitude transformer through threads; and a wave node of the amplitude transformer is arranged on the shell by welding. The piezoelectric ultrasonic salt-bath heating nitriding device has the advantages of compact and simple structure, improved nitriding rate and efficiency, safe and reliable working, high economical efficiency and the like; and in nitriding process production, the piezoelectric ultrasonic salt-bath heating nitriding device can efficiently perform chemical heat treatment on various metallic materials, and can be widely applied in the field of machine building.