Door structure of heat treatment furnace

A door structure of a heat treatment furnace performing a heat treatment of a workpiece, the door structure comprising:

• a first opening member and a second opening member in which workpiece passing ports where a transferred workpiece passes are formed;
• and
• a sheet shutter which blocks outward flow of furnace interior atmosphere by raising and lowering a sheet material, wherein
• the first opening member and the second opening member are disposed to face each other, and
• the sheet shutter comprises:
• a winding portion which winds the sheet material;
• and
• a shutter portion which is raised and lowered by an action of the winding portion, wherein
• the shutter portion is disposed between the first opening member and the second opening member and has a first sheet portion which covers the workpiece passing port of the first opening member and a second sheet portion which covers the workpiece passing port of the second opening member at a time that the shutter portion is lowered, and
• it is configured that a gas storage portion in which gas flowing from a furnace interior is stored is formed between the first opening member and the second opening member at the time that the shutter portion is lowered.