The present invention discloses a mode multiplexer/demultiplexer and a switching node. The mode multiplexer/demultiplexer includes a multi-mode optical waveguide, a first transmission optical waveguide, and a second transmission optical waveguide. The multi-mode optical waveguide includes a first mode channel and a second mode channel. The first transmission optical waveguide includes a first coupling region that includes a first fundamental-mode channel, and the first fundamental-mode channel performs optical mode coupling with the first mode channel in the multi-mode optical waveguide. The second transmission optical waveguide includes a second coupling region that includes a second fundamental-mode channel, and the second fundamental-mode channel performs optical mode coupling with the second mode channel in the multi-mode optical waveguide. An effective refractive index of a fundamental-mode optical signal in the first coupling region is different from an effective refractive index of the same fundamental-mode optical signal in the second coupling region.