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 photodiodes (4) are formed in array form on a surface at a side of an n-type silicon substrate (3) onto which light to be detected is made incident and 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 a transparent resin film (6), which covers the formed regions of the photodiodes (4) and transmits the light to be detected, provided at the incidence surface side.