Abstract: A semiconductor light detecting element includes: a semiconductor substrate; and a distributed Bragg reflector layer of a first conductivity type, an optical absorption layer, and a semiconductor layer of a second conductivity type, sequentially laminated on the semiconductor substrate. The distributed Bragg reflector layer includes first and second alternately laminated semiconductor layers with different band-gap wavelengths, sandwiching the wavelength of detected incident light. The sum of thicknesses a first and a second semiconductor layer is approximately one-half the wavelength of the incident light detected.