A system for supporting and rotating substrates in a process chamber comprising a first exhaust vacuum pump for exhausting the process chamber, a shaft vertically extending into the process chamber to support wafers in it, bearings for supporting the shaft rotatable, a mechanism for rotating the shaft together with the wafers, a bearing casing for covering the bearings and communicated with the process chamber, a second exhaust vacuum pump for exhausting the bearing casing, and a controller for controlling the first and second exhaust vacuum pumps in such a way that the bearing casing is exhausted by the second exhaust vacuum pump before the process chamber is exhausted by the first exhaust vacuum pump.