PURPOSE: To improve a photoelectric transfer effectiveness by composing an incident light window in which at least one part of the window is comprised of an optical fiber plate in which each fiber is tilted to a photoelectricity surface.

CONSTITUTION: An optical fiber plate 5, having a thickness of 1 mm and each fiber 6 has a diameter of 5 μm, is sticked by adhesives to the incident side of a glass plate 3 in an incident light window 1 of a photoelectric transfer tube. The axis 1 of the optical fiber 6 is tilted by an angle θ to an incident glass window. Antimony and plural kinds of alkaline metals are metalized to a vacuum vessel 11 surface of the glass window 3, and serves as a multi alkaline photoelectric surface 8. The incident light I to the photoelectric transfer tube reaches to the photoelectric surface 8 via the optical fiber 6 and the glass plate 3. The optical path of the incident light T becomes longer and the ratio of which photon is changed to photoelectron becomes higher as the incident light T to the photoelectric surface 8 is tilted to the photoelectric surface 8.