A headphone set is equipped with left- and right-ear headphone units. Each unit includes a housing body having a first plane section and a second plane section that faces the first section, the sections being almost perpendicular to a cross section of a cavum conchae of a user's ear when the housing body is fit in the cavum conchae, a speaker and a microphone aligned between the sections, the speaker being located at the first section side, the microphone being located at the second section side. A sound output section is provided at the first section, to give off sounds output by the speaker to an outer space of the housing body. A sound pick-up hole is provided at the second section, through which the outer space communicates with an inner space of the housing body created between a sound pick-up section of the microphone and the second section.