A headphone includes a housing, a light emitting device and a printed circuit board. The light emitting device is mounted in the housing. The light emitting device includes a luminous unit, and a light guiding unit disposed close to the luminous unit. The light guiding unit has a base portion, an incident surface formed at an inner surface of an inner end of the base portion, an emitting surface formed at an outer surface of an outer end of the base portion, a first refracting surface, a first reflecting surface, a second reflecting surface, a second refracting surface, a light transmitting column, a positioning wall, an upper buckling arm and a lower buckling arm. The printed circuit board is mounted in the housing.