PURPOSE: To enable a wafer treating system in which a plurality of wafer treating devices are arranged in parallel along the running passage of carrying trucks which carry cassettes housing wafers to eliminate the interference between the maintenance attendants and the trucks so that the maintenance work by the attendants and cassette carrying work by the trucks can be performed completely independently, safely, and efficiently.

CONSTITUTION: The cassette receiving sections 5 and 15 and cassette feeding sections 6 and 16 of wafer treating devices 1 and 2 are arranged beside the running passage L of carrying trucks and, at the same time, the treating mechanisms 7 and 17 of the devices 1 and 2 are laterally arranged against the passage L and an attendant area A is set on the opposite side of the device 1 and 2 with respect to the passage L.