Heat treatment furnace and heat treatment method

A heat treatment furnace used to anneal a workpiece to be heat-treated, the heat treatment furnace comprising:

• a heating chamber configured to heat the workpiece;
• a first cooling chamber configured to cool the workpiece having passed through the heating chamber;
• a second cooling chamber that is located on a downstream side of the first cooling chamber in a conveying direction of the workpiece and that is configured to cool the workpiece having passed through the first cooling chamber;
• and
• an atmosphere gas supply device configured to supply, as an in-furnace atmosphere gas, an exothermic converted gas to each of the first cooling chamber and the second cooling chamber,
• wherein
• the first cooling chamber has a first cooling state of cooling the workpiece by using a first coolant and a second cooling state of cooling the workpiece by using not the first coolant but a second coolant different from the first coolant, and
• the second cooling chamber has a third cooling state of cooling the workpiece by using a third coolant and a fourth cooling state of cooling the workpiece by using not the third coolant but a fourth coolant different from the third coolant.