To prevent the occurrence of trouble such as deformation and crack, in a substrate by successfully absorbing thermal expansion of the substrate when such thermal expansion arises in the substrate at the time of treating the substrate.

This substrate holder is designed to support the thin sheet-like substrate 2 of a square shape and its substrate supporting surface 22 has a base 20 which is formed as a cylindrical recessed surface and plural coil springs (elastic bodies) 34 which press the end faces of non-curved two sides 5, 6 of the substrate 2 on the substrate supporting surface 22 inward along the substrate supporting surface 22.