An electron tube comprising: a photoelectric conversion part (3, 3A, 3B) that is configured to emit electrons corresponding to incident light; an electron detection part that is disposed to face the photoelectric conversion part (3, 3A, 3B), and is configured to receive the electrons; a focusing electrode part that includes an electrode plate disposed between the photoelectric conversion part (3, 3A, 3B) and the electron detection part, and is configured to accelerate and focus the electrons from the photoelectric conversion part (3, 3A, 3B) toward the electron detection part; and a casing (2, 2D) that includes a stem part (9, 9D, 9E) provided with the electron detection part, and forms an internal space in which the photoelectric conversion part (3, 3A, 3B) and the electron detection part are disposed and which is maintained in a vacuum, wherein the stem part (9, 9D, 9E) is provided with a light incident window portion (26, 26D, 26E) through which the light is transmitted, and includes a light-shielding part that is configured to light-shield the periphery of the light incident window portion (26, 26D, 26E), the electrode plate includes a first region provided with a light passage portion that is configured to guide the light to the photoelectric conversion part (3, 3A, 3B) by allowing the light guided from the light incident window portion (26, 26D, 26E) to be transmitted, and a second region provided with an electron passage portion that is configured to guide the electrons to the electron detection part by allowing the electrons emitted from the photoelectric conversion part (3, 3A, 3B) to be transmitted, the first region is formed on a first axial line that connects the light incident window portion (26, 26D, 26E) and the photoelectric conversion part (3, 3A, 3B), the second region is formed on a second axial line that connects the photoelectric conversion part (3, 3A, 3B) and the electron detection part, characterized in that the light passage portion is spaced away from the electron passage portion. a photoelectric conversion part (3, 3A, 3B) that is configured to emit electrons corresponding to incident light; an electron detection part that is disposed to face the photoelectric conversion part (3, 3A, 3B), and is configured to receive the electrons; a focusing electrode part that includes an electrode plate disposed between the photoelectric conversion part (3, 3A, 3B) and the electron detection part, and is configured to accelerate and focus the electrons from the photoelectric conversion part (3, 3A, 3B) toward the electron detection part; and a casing (2, 2D) that includes a stem part (9, 9D, 9E) provided with the electron detection part, and forms an internal space in which the photoelectric conversion part (3, 3A, 3B) and the electron detection part are disposed and which is maintained in a vacuum, wherein the stem part (9, 9D, 9E) is provided with a light incident window portion (26, 26D, 26E) through which the light is transmitted, and includes a light-shielding part that is configured to light-shield the periphery of the light incident window portion (26, 26D, 26E), the electrode plate includes a first region provided with a light passage portion that is configured to guide the light to the photoelectric conversion part (3, 3A, 3B) by allowing the light guided from the light incident window portion (26, 26D, 26E) to be transmitted, and a second region provided with an electron passage portion that is configured to guide the electrons to the electron detection part by allowing the electrons emitted from the photoelectric conversion part (3, 3A, 3B) to be transmitted, the first region is formed on a first axial line that connects the light incident window portion (26, 26D, 26E) and the photoelectric conversion part (3, 3A, 3B), the second region is formed on a second axial line that connects the photoelectric conversion part (3, 3A, 3B) and the electron detection part, characterized in that the light passage portion is spaced away from the electron passage portion.