A method of cooling a heat treatment bath of melted salt into which heat is being introduced through the quenching of hot workpieces, the heat being removed from the salt bath through the introduction of a partially evaporated cooling medium, preferably water, whose complete evaporation takes place in direct contact with the melted salt, a portion of the latter being at the same time entrained in a circulatory flow out of the treatment tank and back into it, thereby agitating the salt bath for temperature equalization. The device includes a heat exchanger immersed in the salt bath for the partial evaporation of the cooling medium, and a circulation pipe for direct contact of the cooling medium with the melted salt.