A streak tube device for electrically slitting the image of an object provided by an optical system. The streak tube device includes a streak tube body having a photoelectric conversion device for receiving the object image and producing a corresponding electron image. The streak tube device further includes focusing apparatus for focusing the electron image, electrical slitting apparatus for transmitting a selected portion, that is, slit images of the electron image, apparatus for controlling the electrical slitting apparatus, and focusing apparatus for focusing slit images on a fluorescent surface included within the streak tube body. The electrical slitting apparatus of the streak tube device includes a slit member having a slit which extends across the streak tube body, shift electrodes for vertically shifting the transmitted electron image, and a circular collimator for collimating the shifted electron image and transmitting the collimated electron image through the slit to form a slit image.