A packaging box is provided, which comprising a box body with a top opening and an openable cover connected at a top of the box body. The box body comprises a bottom wall and a side wall connected to a peripheral edge of the bottom wall, and a top of the side wall forms an arc top edge folding outward. The openable cover further comprises a top wall and a fastening part connected to a peripheral edge of the top wall. A convex rib is formed on the fastening part which matches with the arc top edge. The convex rib blocks at a lower edge of the fastening part. A concave recess is respectively arranged on opposite sides of the side wall. The sealing performance as well as the strength of the packaging box is effectively improved, while the structure of the packaging box is convenient for operation.