An optical network system includes a first node that converts input signals of n systems into optical signals having wavelengths different for each of the systems and wavelength-multiplexes and transmits the optical signals and a second node that selects signals of n systems from the wavelength-multiplexed signals and outputs the signals. The first node includes an optical coupler that divides the input signals into operating system signals and redundant signals, TPNDs that convert the operating systems into optical signals, an optical switch that selects standby system signals from the redundant signals, and a TPND that converts the standby system signals into optical signals in a storage mode corresponding to a type of the standby system signals. The second node includes TPNDs that convert the optical signals converted from the operating system signals into signals of a type corresponding to the input signals, a TPND that converts the optical signals of the standby system signals into signals of the type of the input signals in a storage mode corresponding to the standby system signals, and an optical switch that selects an output destination of the signals output from the TPND.