A substrate holder prevents a substrate to be bent or damaged owing to inward declining of a seal lip. The substrate holder with an opening includes a seal, and a seal support which has a seal support surface, and is formed on an outer circumference of the opening. The seal includes a seal body and a seal lip. At least a part of the seal support surface has an inclination angle that allows an inner end of the seal support surface to approach the plane on which the substrate is to be positioned. The inner end of the seal support surface is positioned on an inner side than the seal lip.