In a method for manufacturing an electron tube including a front substrate and a back substrate, a wiring and an electrode are formed on the front substrate and/or the back substrate. A component is mounted on the front substrate and/or the back substrate. A ring-less getter is mounted on at least one of the front substrate, the back substrate and the component. A vessel is assembled and sealed so that the front substrate faces the back substrate. A light is irradiated on the ring-less getter from outside of the sealed vessel, thereby activating the ring-less getter.