An ignitor comprising a casing, an ignition coil (1) disposed within the casing (20), a power-transistor package (26) disposed within the casing (20) and electrically connected to the ignition coil (1) for interrupting an electric current flowing through the ignition coil (1), an electrical connector (21) mechanically attached to the power-transistor package (26) and for electrically connecting the ignition coil (1) and the power transistor package (26) to an external circuit and an electrically insulating resin (28) filled within the casing for hermetically sealing and supporting therein the ignition coil (1) and the power-transistor package (26). The power transistor package (26) may comprises a holder (23) mounting the mold resin package and electrically connecting the electrical connector (21) to the power-transistor package (26) and the electrical connector (21) may be fixed to the holder (23) by fastening means (22, 24).