A microphone includes a polar piece contacting with a first magnetic pole of a first permanent magnet, a yoke body annularly arranged around the polar piece through a magnetic gap G with a predetermined width, a magnetic circuit unit including a tail yoke connected to the yoke body and contacting with a second magnetic pole of the first permanent magnet, and a diaphragm unit provided with a voice coil arranged to vibrate in the magnetic gap. The second magnetic pole of the first permanent magnet contacts with one side of the tail yoke, a first magnetic pole of the second permanent magnet is disposed to contact with other side of the tail yoke, a magnetic path is produced between the second magnetic pole of the second permanent magnet and the yoke body, and the first permanent magnet and the second permanent magnet are polarized in the same sense.