Tray and heat treatment method

A tray for conveying a workpiece placed on the tray inside a heat treatment furnace, the tray comprising:

• a plurality of positional displacement regulating parts having inside spaces with different sizes for respectively receiving plural kinds of workpieces with different sizes into the inside spaces so as to be supported on a corresponding bottom supporting surface of the respective inside spaces and for respectively regulating horizontal positional displacements of the plural kinds of workpieces, wherein the plurality of positional displacement regulating parts are arranged concentrically in a plane shape;
• and
• a through hole in communication with the inside spaces of the plurality of positional displacement regulating parts and penetrating the tray in a vertical direction of the tray.