A panel having positioning function includes a body covering an opening on an extrusion casing, and a positioning mechanism having at least one position set. The position set includes a first rib disposed on a first side of the body, a first contact portion disposed on the first rib and contacting against an inner surface of the extrusion casing, a second rib disposed on a second side of the body, and a second contact portion disposed on the second rib and contacting against the other inner surface of the extrusion casing. A position of the second rib on the second side is symmetrized to a position of the first rib on the first side, so that the panel can align with the extrusion casing due to deformation of the position set.