A rinsing water supply system for supplying water to a rinsing unit of a developing apparatus in which photosensitive materials are processed and rinsed. The water supply system includes a pipe having a water supply passage through which water is introduced into the rinsing unit from a water source, a solenoid valve for opening and closing the water supply passage, and signal lines arranged along and integrally with the pipe and adapted for transmitting signals for operating the solenoid valve. This arrangement eliminates the necessity for installation of a signal transmission line independently from the water supply passage, for the purpose of transmitting signals for operating the solenoid valve.