Placement board and placement structure

A placement structure comprising:

• a workpiece;
• a placement board including a main body unit configured to form a flow channel for circulation of a medium for heat exchange and place the workpiece thereon, the main body unit being made of a metallic material;
• and
• a heater provided in an outer edge region of the main body unit, wherein
• in a state where the heater has been driven and the medium has been caused to circulate through the flow channel, a temperature difference between the outer edge region and an inner region of the main body unit at a surface of the main body unit where the workpiece is placed is 20° ° C. or more, and
• a temperature difference between a lowest temperature and a highest temperature of the workpiece in a state where the workpiece has been placed on the placement board is 20° C. or more.