When light is made incident into antenna layers 11a, 11b, and 11c of a photodetector 1, specific wavelength components of light contained in the incident light combine with surface plasmons of the antenna layers 11a, 11b, and 11c, and surface plasmon resonance occurs. Thereby, near-field lights are outputted from through-holes 13 of the antenna layers 11a, 11b, and 11c. The near-field light outputted from each through-hole 13 reaches a light absorbing layer 4 via light receiving surfaces 4a, 4b, and 4c. The light absorbing layer 4 generates a charge of an amount according to the amount of received light. Since cycle intervals Λa, Λb, and Λc of convex portions 12 in the antenna layers 11a, 11b, and 11c are different from each other, the wavelength component of light that combines with a surface plasmon differs in each of the antenna layers 11a, 11b, and 11c. Consequently, a plurality of wavelength components of light can be detected.