An optical network system capable of directly routing optical signals without entailing multiple reception of identical wavelengths. A set wavelength output unit outputs a set wavelength. An Nk-axis filter receives an Nk-axis signal propagated through a ring of an Nk-axis direction and an Nk−1-axis signal split inside the local node, and performs filtering by removing a wavelength identical with that of the Nk−1-axis signal from the Nk-axis signal and adding the wavelength of the Nk−1-axis signal to the Nk-axis signal. An Nk-axis splitter splits the Nk-axis signal into two, one being output to outside through the ring of the Nk-axis direction while the other being output, if k