A wavelength splitting element for splitting a multiplexed light beam into separate wavelength bands and emitting the beams from separate emission ports including a first filter for splitting the multiplexed light beam into light beams in wavelength band λ1, which passes in a first direction, and wavelength bands λ2 and λ3, which reflects; a second filter, for splitting the reflected light into light beams in wavelength band λ3, which passes in a second direction, and wavelength band λ2, which reflects in a third direction; and a third filter, for passing the light beam in the wavelength band λ2. The first filter passes the light beam in the wavelength band λ2 reflected by the second filter and incident to the first filter again based on an incident angle, and the third filter passes only the light beam in the wavelength band λ2 that the first filter passes in the third direction.