A child safety seat is for use on a vehicle seat. The vehicle seat has a safety belt. The child safety seat includes a seat base, a seat panel, and a seat body. The seat base has a seat assembly portion and a backrest portion. The seat panel is openably pivoted to the seat assembly portion for rotating between an open position and a closed position. The seat body is disposed on the seat panel. When the seat panel rotates to the open position, the safety belt passes over the seat base for attaching the seat base to the vehicle seat. When the seat panel rotates to the closed position, the seat panel clamps the safety belt cooperatively with the seat base.