Provided is an earphone, including an earphone body and an earphone cap. The earphone body includes an earphone shell forming a sound cavity and disposing a sound-guiding pipe. The sound-guiding pipe disposes at least one through hole. The earphone cap is rotatably mounted on the earphone body and includes a main body and a barrel. The barrel is located on the inside of the main body and arranged to encompass the sound-guiding pipe. The barrel disposes at least one opening, which is arranged to be aligned or misaligned with the part or whole of the through hole. The earphone of the present invention can make the opening be aligned or misaligned with and the part or whole of the through hole by rotating the earphone cap, thereby varying the pressure of the sound cavity to attain the object of adjusting sound effect.