An screw assembling device includes a supplying mechanism, a securing mechanism, a driving mechanism, and an assembling mechanism. The supplying mechanism supplies a number of screws sequentially. The securing mechanism holds a housing of an electronic device. The assembling mechanism is connected to the supplying mechanism and the driving mechanism. The assembling mechanism is driven by the driving mechanism to predetermined positions of the housing of electronic device and is configured for assembling the plurality of screws transmitted from the supplying mechanism to the predetermined positions of the housing of electronic device.