A screw mounting jig. The jig supports an electronic device thereon. The electronic device includes a first surface and a second surface opposite to the first surface. A first screw hole is formed on the first surface, and a second screw hole is formed on the second surface. The jig includes a base and a supporting assembly. The electronic device is received in the supporting assembly. The supporting assembly is disposed on the base in a manner such that it rotates between a first position and a second position. When the supporting assembly is located at the first position, the first surface faces the base so that the second screw hole is exposed for insertion. When the supporting assembly is located at the second position, the second surface faces the base so that the first screw hole is exposed for insertion.