Heat treatment furnace

A heat treatment furnace having:

• a furnace body having a doored opening;
• a hearth which is opposed to an interior of said furnace body;
• a blowing apparatus which is placed inside said furnace body, and which takes in a gas in the furnace body to blow wind:
• a wind passing member which is placed inside the furnace body, which is opposed to said blowing apparatus, and through which the wind passes;
• a heating apparatus which is placed inside said furnace body, and which heats at least one of the gas taken in by said blowing apparatus, and wind that has not yet entered said wind passing member;
• and
• a rack which is placed inside said furnace body and in a circumference of said wind passing member, and which rotates around said wind passing member, wherein
• said wind passing member has:
• a cylindrical portion having an entrance port through which the wind enters, and rack-opposing flow-out ports which are opposed to said rack, and through which the wind flows out;
• and
• wind guiding portions which are attached to said cylindrical portion, and which block part of the wind flowing along an inner circumferential surface of said cylindrical portion, to guide the wind to the rack-opposing flow-out ports.