To require no parts such as engaging pieces which need to be previously attached to an open showcase and make an engaging structure applicable to an open showcase made of a material to which a magnet is not attracted.

In the engaging structure of a winding cover for the open showcase, the winding cover 5 is engaged with the corner 3 of the open showcase having a surface 3a intersecting the drawing direction A of a shield material drawn from a winding case. An engaging member 6 pressed to the intersecting surface 3a by the winding force F of the shield material 2 and a slip stopper 7 provided between the intersecting surface 3a and the engaging member 6 and fixed to the engaging member 6 are provided. The engaging member 6 is engaged with the corner 3 by using the winding force F of the shield material 2.