Provided is an earmuff that has a small size and a light weight, has an excellent sound insulating performance, is capable of blocking a specific frequency band, and has excellent air permeability. The present invention is provided with a headband and two ear cups each having: a housing that is attached to an end of the headband; and an ear pad that is latched to the housing, wherein the housing has a housing opening part and has a sound insulation structure which is disposed in the housing opening part and capable of blocking the sound in a specific frequency band, and the housing opening part having the sound insulation structure disposed therein has a ventilation hole.