In a unidirectional dynamic microphone unit, a cylindrical tube is provided to cover the microphone unit, a cylindrical wall of a first cylindrical portion that is included in the cylindrical tube and extends to at least the rearward is provided with a rear sound wave introducing portion weighted such that an acoustic resistance value is gradually made smaller toward the rearward side from positions of sound holes for taking in a sound wave transmitting around from the rearward side, preferably formed of a trumpet-shaped opening, and it is possible to enhance the sensibility to sound pressures without degradation of the frequency response and the directionality.