A theme is to prevent the generation of noise due to damage in a photodetecting portion in a mounting process in a photodiode array, a method of manufacturing the same, and a radiation detector. In a photodiode array, wherein a plurality of the photodiodes (4) are formed in array form on the surface at a side of the n-type silicon substrate (3) onto which light to be detected is made incident and the penetrating wirings (8), which pass through from the incidence surface side to the back surface side, are formed for the photodiodes (4), the photodiode array (1) is arranged with the spacer (6), having a predetermined planar pattern, provided at non-forming regions of the incidence surface side at which the photodiodes (4) are not formed.