The photomultiplier tube 1 is provided with an upper frame 2 and a lower frame 4 which are arranged so as to oppose each other, with the respective opposing surfaces 20a, 40a made with an insulating material, a side wall part 3 which constitutes a casing together with the frames 2, 4, a plurality of stages of electron multiplying parts 33 which are arrayed so as to be spaced away sequentially from a first end side to a second end side on the opposing surface 40a of the lower frame 4, a photocathode 41 which is installed on the first end side so as to be spaced away from the electron multiplying parts 33, converting incident light from outside to photoelectrons, an anode part 34 which is installed on the second end side so as to be spaced away from the electron multiplying parts 33 to take out electrons multiplied by the electron multiplying parts 33 as a signal, and a wall-like electrode 32 which is arranged so as to enclose the photocathode 41 when viewed from a direction directly opposite to an opposing surface 401 and having a notched part 35 at a site opposing the electron multiplying parts 33 on the second end side.