A dynamic microphone unit has a diaphragm 5 vibrating in response to sound waves, a voice coil 6 fixed to the diaphragm 5 and vibrating in cooperation with the diaphragm 5, a magnetic circuit including a magnetic gap around the voice coil 6 and generating a magnetic field in a magnetic gap, a first air chamber 11 adjacent to the reverse of the diaphragm 5 holding an acoustic resistance therein, a second air chamber 9 behind the voice coil, and a communication passage 22 for sound waves between the first air chamber 11 and the second air chamber 9.