A car cover has a bag for storing the cover. The bag can be stably mounted on the trunk, and in this state the cover can be put on the car smoothly. A pair of triangular sheets are connected to the bag. The bag is secured to the cover member through a gusset provided between the triangular sheets. A belt connected to the free ends of the triangular sheets is put around the hinges in the trunk room. A mounting sheet is stitched to the edge of the opening of the bag and is fastened to the interior surface of the trunk by hook-and-loop fasteners provided near its front edge. After supporting the bag on the rear wall of the trunk by fastening the triangular sheets and the mounting sheet, the trunk door is closed and the cover member is taken out of the bag and put on the car. The locking mechanism of the trunk door can pass through a gap between the triangular sheets or a hole formed in the mounting sheet, so that the trunk door can be closed and locked.