A focusing mechanism for focusing a lens module includes a base seat, a movable platform, a positioning assembly, a support bracket and a plurality of arms. The positioning assembly is fixed to the base seat and passes through a center of the movable platform, a lens of the lens module is detachably mounted on the positioning assembly. The support bracket is fixed to the movable platform. A sensor of the lens module is detachably mounted on the support bracket. Each of the plurality of arms rotatably interconnects the movable platform and the base seat, the movable platform drives the support bracket to rotate relative to the positioning assembly to enable the lens to rotate relative to the sensor via a drive of the arms.