A screw assembly includes a screw, a spring, and a mounting panel. The screw comprises a head portion and a shaft portion extending from the head portion. The spring comprises a spring body and a securing end extending from the spring body. The spring body defines a surrounding opening. The mounting panel defines a through hole corresponding to the surrounding opening. The mounting panel comprises a positioning portion. The shaft portion is located in the surrounding opening and the through hole. The spring is located between the head portion and the mounting panel. The positioning portion is configured to resist the securing end to prevent the spring from rotating.