To reduce the blocking rate of a treatment solution by a method wherein a chamfer section is provided on the circumferential part on the lower side of a notched part and a nozzle, which feeds a treatment solution to the lower surface of a substrate passing through the notched part of a rotating plate.

A spin base 11 is a tabular body provided with a plurality of arms 35, which extend radially at prescribed intervals, and notched parts 36, to be used to pass a treatment solution sent from a chemical solution nozzle and a pure water nozzle provided on the lower part, are provided between the adjacent arms 35. The area of aperture opened to the lower surface of the notched parts 36 can be increased by R-chamfering the edge part of the arms 35. As a result, the quantity of treatment solution to the wafer can be increased, the utilization efficiency of the treatment solution can be improved, and the treatment efficiency to the wafer can also be improved. Also, the treatment efficiency to the notched part of the arms 35 can be improved by chamfering the edge part in the round form. Also, the durability with respect to the notched part of the arms 35 can be improved by chamfering the edge part in the round form. As a result, the durability of the spin base 11 is increased sharply, and the life of the spin base 11 can be prolonged.