Provided is an apparatus for sealing an arc-tube including a jig body including an electrode pin hole into which an end part of the electrode pin inserted into a bypass tube part of the arc-tube is inserted and a connection path connected with the electrode pin hole; and a pressurizing means inserted into the connection path to pressurize and fix the electrode pin positioned at the electrode pin hole. Therefore, the apparatus for sealing an arc-tube can more easily and stably fix the electrode pin during a sealing process.