To provide a heat treatment apparatus wherein prior art heat treatment apparatus is improved, and it can provide required preferred mechanical properties for respective portions of a metal article, without increasing the installation cost.

A heat treatment apparatus is provided, which is adapted such that a multi-layer heat treatment furnace 1 is used with one layer of the multi- layer comprising a particulate structure as a fluidized bed layer 2 which is superior in heat efficiency and uniformity of a thermal distribution, and with an atmospheric layer 3 comprising a gas formed as the other layer. Each of the layers 2, 3 has different temperatures, and a part of a workpiece that is an article to be heat treated is immersed in the fluidized layer 2 at a prescribed temperature, with the other part of the workpiece exposed to the atmospheric layer 3 at a prescribed temperature for heat treatment.