PURPOSE: To facilitate the production of a heat-insulating panel filled with a core material, between skins formed of two metallic sheets, to keep the strength of fitting from being loosened at the place where a fitting projection part is fitted into a recess part to be fitted, and to heighten strength for attaching a member, e.g. a frame member, to the panel, utilizing such structure effectively.

CONSTITUTION: For a skin 1 on one side of a panel, side end face areas 4, 4 each corresponding to both end parts in the cross direction of the panel are bent. On one side 4 thereof, a fitting projection part 7 ranging over the whole length of the panel, from upper to bottom, is formed by bending, and on the other side 4 thereof, a recess part 11 to be put on the fitting projection 7 is formed by bending. An end part 5 being allowed to go round to the surface of the skin side on the other side of the panel is extended from the top end of each of the side end face areas 4, 4, and the top end of the end part 5 is folded back on the inner-surface side thereof, and a folded part 6 to be engaged is formed. On the other hand, for a skin 2 on the other side of the panel, both end parts are folded back inward, and at the top end of each of folded parts 8 of the skin 2, an engaging part 9 is formed by being bent almost in the shape of a letter S. The end parts 5 of the skin 1 each are laid on the folded parts 8 of the skin 2, and the engaging parts 9 each are engaged with the folded parts 6 to be engaged.