A steak tube 1 has a container 2 with an entrance plate 2a and an output plate 2b; a photocathode 7 disposed in the container 2 and configured to emit electrons according to light to be measured, the light having been incident through the entrance plate 2a; a mesh electrode 3, a first focusing electrode 4, and an aperture electrode 5 forming an axially symmetric electron lens for focusing the electrons emitted from the photocathode 7, toward the output plate 2b; a sweep electrode 6 disposed in the container 2 and configured to sweep the electrons focused by the axially symmetric electron lens, in a sweep direction along the output plate 2b; and a second focusing electrode 9 disposed between the entrance plate 2a and the output plated 2b and forming a one-dimensional electron lens for focusing the electrons in the sweep direction.