To provide a substrate processing unit, a substrate transfer method, a substrate cleansing process unit, and a substrate plating apparatus that make it possible for a substrate carry-in mechanism such as a robot arm to quickly release hold on the substrate after carrying in the substrate so as to shorten the time for holding the substrate and improve throughput. The substrate processing unit 10 includes a substrate holding mechanism 10 for holding the substrate 11 in a specified holding position, and a processing mechanism 32 for applying a specified process to the substrate held with the substrate holding mechanism in which a substrate guide mechanism 20 is provided with a guide pin 15 for guiding the substrate to vicinity of a holding position. The substrate holding mechanism has a plural number of rollers 14 on an outer periphery of the holding position of the substrate, with the plural number of rollers adapted to hold the substrate by supporting the periphery of the substrate from sides thereof in the vicinity of the holding position, and the roller has an integral structure made up of a large diameter portion and a small diameter portion formed above the large diameter portion, with an upper portion of the large diameter portion having a shoulder portion for the substrate in transfer to be temporarily placed on, and with the shoulder portion formed with a sloped surface sloping down toward its periphery.