To provide a heat treatment apparatus for heat-treating a steel bar, which spends a constant and extremely short period of time between works of extracting the steel bar from a heating furnace and charging it into a cooling pond, so as to obtain an expected heat treatment effect.

This heat treatment apparatus comprises: a heating furnace having a furnace body with a necessary length for heating the steel bar; a cooling pond which is placed on an extended line of a doorway of the heating furnace, is filled with a coolant, and has a length necessary for cooling a heated steel material; a tray for entering into and leaving from the inside of the heating furnace, in a state of mounting a material to be heat-treated thereon; a pair of chains that run in parallel to each other and a driving means therefor, which are placed on the cooling pond, charges the tray into the heating furnace and extracts it from the heating furnace; and a pair of elevating devices which are placed on both ends of the cooling pond, support the extracted tray and the heated steel material mounted thereon, charge them into the coolant and raise them therefrom.