To surely find a poorly filled place during the placing of concrete in the construction of a reinforced concrete skeleton, in use as lagging for reinforced concrete construction, and to enhance the strength of the reinforced concrete skeleton by suppressing the excessive discharge of moisture and a mortar content in the concrete.

This panel 1 for the concrete form, as the lagging, comprises a membrane material 2 which is transparent or becomes transparent when coming into contact with the moisture in the concrete, and a shape retaining material 3 which is superposed on the membrane material 2 so as to retain the shape of the membrane material 2. The shape retaining material 3 is equipped with a net part 30 with many openings 3b.