A substrate processing device includes a holding member for holding a substrate, and an opposed member having a body portion and an extended portion extending from at least a part of a peripheral edge part of the body portion. A protrusion is provided on one part of a tip side part of the extended portion and a side surface part of the holding member, and the other part is provided with a restricting structure disposed opposite to the protrusion and restricting relative motion of the protrusion. The relative motion between the holding member and the opposed member is restricted, and the substrate processing device further includes a rotating mechanism, and a nozzle for discharging a processing solution and the protrusion and the restricting structure are disposed below an upper surface of the holding member.