PURPOSE: To maintain the uniformity of the photoelectric conversion sensitivity and obtain the higher photo sensitivity by constituting the surface of an incident face plate on which a photoelectric cathode is provided as a diffuse transmission face.

CONSTITUTION: A photoelectric cathode 2 is formed on the back of an incident face plate 1a constituting part of a vacuum container 1. The outside of the incident face plate 1a is formed in the obscured glass, thereby the light direction is changed, and the light is allowed to enter from all directions, while the incident angle to the photoelectric cathode 2 face has been a right angle so far. Thereby, the distance in which the light passes through the photoelectric cathode 2 can be made long in average without increasing the thickness of the photoelectric cathode 2. As a result, light absorption and electron conversion can be increase. Accordingly, photo sensitivity can be improved without increaing the dark current.