A wavelength multiplexer and de-multiplexer includes: a reflection member; a first port provided in the reflection member; a plurality of second ports provided in the reflection member to be spaced apart from the first port; and an optical filter on an optical path between the first port and the plurality of second ports, wherein a plurality of reflection surfaces inclined with respect to the optical filter are formed in the reflection member, a distance of a reflection point from the optical filter in each of the plurality of reflection surfaces becomes smaller as a reflection angle in each of the plurality of reflection surfaces is increased, and each of the plurality of second ports is positioned on a path of light reflected by each of the plurality of reflection surfaces.