The present invention is directed to an optical node apparatus in which the number of light elements that propagates reference light is reduced, which includes pa input-side wavelength mux/demux elements, a switch module, pb output-side wavelength mux/demux elements, and a reference light source. Each of the input-side wavelength mux/demux element include at least two first port and at least two second port. One of the first ports included in each input-side wavelength mux/demux element is coupled to an input transmission path. The other of the first ports coupled to the reference light source, and each of the second ports is coupled to an input end of the switch module.