A cleaner for magnetic heads of tape recorders includes two gears centrally engaged with the revolving shaft of the recorder during use and pivotally installed in two revolving shaft holes on the tape cartridge respectively and peripherally engaged with each other. A plurality of projecting posts are spaced equally along the circumference in the planes of the two gears and alternately disposed in respect of each other post. A rocker is centrally and pivotally installed nearby the front end of tape recorder and between the two gears. Two opposite contact legs are provided to the rear end of the rocker and projected toward these posts respectively so as to contact these post alternately and respectively, and a cleaning element is installed on the front of the rocker. When this cleaner is installed in the tape recorder for use, the two gears rotate synchronously in opposite directions, the posts push and swing the rocker left and right alternately and respectively in sequence, so the rocker swings left and right and the cleaning element of the front end of rocker can clean the magnetic head of the recorder.