A unidirectional microphone is provided that has an excellent directional frequency response and a high sensitivity. Sound waves are guided to a rear acoustic terminal 10b of an acoustic resistance tube 30 through an acoustic resistance member 31. A rear end opening 30b of the acoustic resistance tube 30 is blocked so as to prevent the sound waves from entering the rear acoustic terminal 10b from the rear end opening 30b of the acoustic resistance tube 30 on the side of the rear acoustic terminal 10b. A gap G which allows low-frequency sound waves to pass and through which a front acoustic chamber A1 and a rear acoustic chamber A2 in the acoustic resistance tube 30 communicate with each other is provided between the inner peripheral surface of the acoustic resistance tube 30 and the outer peripheral surface of the microphone unit 10.