A headphone structure for adjusting audio frequencies is provided, which comprises a front housing, a rear housing, a sound-producing unit in the front housing and an elastic ear-contacting body sleeving the front housing. The front housing has at least one slot or recess, and the elastic ear-contacting body sleeves the front housing to form at least one gap. The headphone structure for adjusting audio frequencies of the present invention has better results for the adjustment of bass frequencies. In addition, the headphone structure of the present invention is not complicated and is easy to manufacture. The headphone structure of the present invention can be applied to various types of headphone, such as in-ear headphones and circumaural headphones.