An antenna device for an automobile comprises an electric heating type defogger having heating strips (2) and an antenna conductor (6) having antenna strips arranged to form a pattern, which are fitted on the rear window glass fitted to a rear window opening formed in an automobile, wherein the defogger (4A) and the antenna conductor (6A) are spaced apart from each other with a predetermined small space in a capacitive coupling relation so that a high frequency current is caused to flow. A reactance circuit (8) is connected to the defogger to effect anti-resonance between the defogger and the rear window opening of the body of the automobile at the central frequency. A quality factor value is determined by the inductance of a chock coil (9) in the reactance circuit and the stray capacitance between the defogger and the rear window opening of the body of the automobile so that the ratio of the input impedance of the receiver to the impedance of the antenna conductor viewed from the side of a power feeding terminal (11) becomes 1; and a matching circuit (13) is inserted between the power feeding terminal (11) of the antenna conductor and the receiver (12).
