A light-absorbing layer is composed of a compound-semiconductor film of charcopyrite structure, a surface layer is disposed on the light-absorbing layer, the surface layer having a higher band gap energy than the compound-semiconductor film, an upper electrode layer is disposed on the surface layer, and a lower electrode layer is disposed on a backside of the light-absorbing layer in opposition to the upper electrode layer, the upper electrode layer and the lower electrode layer having a reverse bias voltage applied in between to detect electric charges produced by photoelectric conversion in the compound-semiconductor film, as electric charges due to photoelectric conversion are multiplied by impact ionization, while the multiplication by impact ionization of electric charges is induced by application of a high-intensity electric field to a semiconductor of charcopyrite structure, allowing for an improved dark-current property, and an enhanced efficiency even in detection of low illumination intensities, with an enhanced S/N ratio.