The present invention relates to an ignition device for exothermic welding comprising an electrically conductive metal bushing (1) that can house a pellet of a first welding material (4) in electrical contact with the inner wall of an inner chamber (1c) of the bushing (1), provided with an electrically insulating cap (2) and a bottom base (1b) with an opening (1d) through which the first welding material (4) falls in an incandescent state onto a second welding material (4a) arranged in a weld mold (7) when an exothermic reaction has been triggered in the first welding material (4); an electrode (5) that goes through the cap (2) of the metal bushing (1) and comprises a top contact (5a) connectable to a power output (24) of a voltage generator and a bottom contact in the form of a filament (5b) that can be in electrical contact with the pellet of the first welding material (4), the filament (5b) being made of a material having a melting temperature greater than the ignition temperature of the welding material (4); as well as a contact-assuring element (3) which is guided into the inner chamber (1c) between the bottom base (1b) and the pellet of the first welding material (4).