The photomultiplier tube 1 is provided with a casing 5 made of an upper frame 2 and a lower frame 4, an electron multiplying part 33 having dynodes 33a to 331 arrayed on the lower frame 4, a photocathode 41, and an anode part 34. Conductive layers 202 are installed on an opposing surface 20a of the upper frame 2. The electron multiplying part 33 is provided with base parts 52a to 52d of the respective dynodes 33a to 33d installed on the side of the lower frame 4, and power supplying parts 53a to 53d connected to the conductive layers 202 at one end parts of the respective base parts 52a to 52d in a direction along the opposing surface 40a. The base parts 52a to 52d are constituted in such a manner that the both end parts are joined to the opposing surface 40a, the central part is spaced away from the opposing surface 40a, and a cross sectional area at the one end part on the side of each of the power supplying parts 53a to 53d is made greater than a cross sectional area at another end part.