An image-forming apparatus is provided with a bookbinding device having a binder receiving portion. The binder receiving portion is provided with a heat source for heating an adhesive or with an electrode for electrifying the electric heating member on a bottom portion thereof so that a plurality of papers disposed in a binder can be adhered to the inner surface of the back cover of the binder by heating and melting the adhesive with the heat source or the electric heating member. The heat source or electrode is swingably mounted in the binder receiving portion for movement between a bookbinding position and a retracted position. An operating mechanism is provided for moving the heat source or electrode from the retracted position to the bookbinding position upon insertion of the binder into the binder receiving portion.