A photodiode array 1 is provided with an n-type silicon substrate 3. A plurality of photodiodes 4 are formed in array on the opposite surface side to an incidence surface of light L to be detected, in the n-type silicon substrate 3. Spacers 6 having a predetermined height are provided in a region not corresponding to regions where the photodiodes 4 are formed, on the incidence surface side of the light L to be detected, in the n-type silicon substrate 3.