An inner module used in a wireless earphone is installed primarily in a wireless earphone, including a circuit loop and an upper cover. The circuit loop includes at least a first circuit board, at least a second circuit board which is extended from the first circuit board, and a lower cover which encloses the first circuit board. The upper cover is installed on the lower cover, including a first side wall which forms an angle with respect to the lower cover. In addition, the first side wall is provided with a first positioning slot to accommodate the second circuit board. Therefore, the inner module is formed into a modularized design to simplify the assembly procedure of the wireless earphone, which reduces the labor cost in assembling the wireless earphone significantly.