To provide a heat treatment apparatus utilizable in a coating line when the surface to be coated of a workpiece pretreated by water washing or the like is dried or when the coated surface of the coated workpiece is dried/baked.

The heat treatment apparatus is composed of: a bottom-open heat treatment furnace 40; heating means (a hot air circulation line 54, a heating means 55, a hot air circulation blower 56 and a controller 57) for heating the inside of the heat treatment furnace 40; a workpiece supporting rack 45 to be positioned just under the heat treatment furnace 40; and an upward/downward driving means 44 for upward/downward moving the work supporting rack 45 relatively to the heat treatment furnace 40 to vertically take the workpiece W supported by the work supporting rack 45 in and out of the heat treatment furnace 40.