A photomultiplier tube comprising: a vacuum vessel having a faceplate constituting one end and a stem constituting another end; a photocathode that converts incident light incident through the faceplate to electrons; an electron multiplying section that multiplies the electrons emitted from the photocathode; and an electron detecting section that transmits output signals in response to electrons from the electron multiplying section, wherein the photocathode, the electron multiplying section, and the electron detecting section are provided within the vacuum vessel, where the electron multiplying section comprises: an electrode-layered unit in which a plurality of multiplying electrodes (Dy1-Dy12) is stacked to form a plurality of stages; potential applying means that applies a predetermined potential to each of the plurality of multiplying electrodes (Dy1-Dy12); and a focusing electrode that converges the electrons emitted from the photocathode to reach the electrode-layered unit, characterized in that cutout portions are formed on peripheral sections of the multiplying electrodes (Dy1-Dy12) and an anode, that planes formed by the cutout portions are stacked in a stacking direction (z) of the multiplying electrodes (Dy1-Dy12), and the potential applying means extends from the stem in the stacking direction (z) of the multiplying electrodes (Dy1-Dy12) and penetrates the planes formed by the cutout portions, and that the focusing electrode is disposed between the electrode-layered unit and the photocathode and covers the cutout portions and the multiplying electrodes (Dy1-Dy12) in the stacking direction (z) of the multiplying electrodes (Dy1-Dy12). a vacuum vessel having a faceplate constituting one end and a stem constituting another end; a photocathode that converts incident light incident through the faceplate to electrons; an electron multiplying section that multiplies the electrons emitted from the photocathode; and an electron detecting section that transmits output signals in response to electrons from the electron multiplying section, wherein the photocathode, the electron multiplying section, and the electron detecting section are provided within the vacuum vessel, where the electron multiplying section comprises: an electrode-layered unit in which a plurality of multiplying electrodes (Dy1-Dy12) is stacked to form a plurality of stages; potential applying means that applies a predetermined potential to each of the plurality of multiplying electrodes (Dy1-Dy12); and a focusing electrode that converges the electrons emitted from the photocathode to reach the electrode-layered unit, characterized in that cutout portions are formed on peripheral sections of the multiplying electrodes (Dy1-Dy12) and an anode, an electrode-layered unit in which a plurality of multiplying electrodes (Dy1-Dy12) is stacked to form a plurality of stages; potential applying means that applies a predetermined potential to each of the plurality of multiplying electrodes (Dy1-Dy12); and a focusing electrode that converges the electrons emitted from the photocathode to reach the electrode-layered unit, characterized in that cutout portions are formed on peripheral sections of the multiplying electrodes (Dy1-Dy12) and an anode, that planes formed by the cutout portions are stacked in a stacking direction (z) of the multiplying electrodes (Dy1-Dy12), and the potential applying means extends from the stem in the stacking direction (z) of the multiplying electrodes (Dy1-Dy12) and penetrates the planes formed by the cutout portions, and that the focusing electrode is disposed between the electrode-layered unit and the photocathode and covers the cutout portions and the multiplying electrodes (Dy1-Dy12) in the stacking direction (z) of the multiplying electrodes (Dy1-Dy12).