To stably obtain high acoustic resistance required for pressure equalization in a non-directional condenser microphone unit.A diaphragm 8 whose circumferential edge is attached to a diaphragm holder 4 and a fixed electrode 6 made of a metal material and arranged to face the diaphragm at a predetermined interval through an electrically insulating spacer 5 are provided, and the rear space of the above-mentioned diaphragm is closed to constitute the non-directional condenser microphone unit. A blind groove 16a is formed by an etching process at a portion which is in contact with the spacer 5 and in the fixed electrode 6 so that the rear space between the diaphragm and the fixed electrode may communicate with the outside, and a communication part formed between the groove 16a and the spacer 5 may be used as acoustic resistance for pressure equalization.