The invention relates to the field of workpiece heat treatment, and discloses a quenching device. The quenching device comprises a quenching tank, a liquid storage tank, a backflow assembly, a liquidsupply assembly and a mist spray assembly, wherein the backflow assembly, the liquid supply assembly and the mist spray assembly are connected between the quenching tank and the liquid storage tank; the liquid supply assembly and the mist spray assembly are used for enabling a water-based quenching medium in the liquid storage tank to flow to the quenching tank; the water-based quenching medium inthe quenching tank back-flows to the liquid storage tank through the backflow assembly; and backflow prevention assemblies are arranged on the liquid supply assembly and the mist spray assembly and are used for preventing the water-based quenching medium in the quenching tank from back-flowing to the liquid storage tank. According to the quenching device, quenching in four ways of water mist spraying, water spraying, water soaking and air cooling is completed, so that the resource utilization rate is improved. The water-based quenching medium is recycled, so that the resource utilization rateis improved. Oil quenching is replaced, so that the cost is reduced, and the safety is improved. Through arranging switch pieces on the backflow prevention assemblies and the backflow assembly, the water-based quenching medium in the quenching tank is favorably prevented from back-flowing to the liquid storage tank, so that a workpiece is ensured to be fully soaked into the water-based quenchingmedium, and the quenching efficiency is improved.