A rotor structure for a motor includes a shaft, a single magnet and two fixing seats. The single magnet has two opposite end faces. An axial hole has a maximum extent equal to a maximum extent between the two opposite end faces. At least one of the two opposite end faces has a first engaging member. The magnet and each opposite end face have a maximum radial extent. Each fixing seat includes an abutting face having a maximum radial extent the same as the maximum radial extent of the single magnet and of the opposite end faces. One of the abutting faces has a second engaging member. The first engaging member is located at the maximum radial extent at the outer edge of the at least one of the two opposite end faces, or located at the inner edge of the at least one of the two opposite end faces.