PURPOSE: To improve workability by installing an engagement part along the longitudinal direction at the edge part of a body in which at least one hollow part is formed along the longitudinal direction and using either of both side surfaces of the body as concrete supporting surface.

CONSTITUTION: At least one hollow part 48 is formed along the longitudinal direction of a panel body 45, and engagement parts 47 and 48 are extended at the edge part, and a center mold frame panel 9, mold frame panel 14 for supporting beam, and a mold frame panel 15 for floor slab are constituted so as to mounted and demounted by a plurality of mold frame panels (a), (b), and (c), Then, the panel 9 is previously fixed with a steel reinforcement beam 4 through a supporting metal fitting 5, etc., on the ground, and an edge thick member and reinforcing members 10 and 11, etc., are suspended, and set at prescribed positions by a crane, etc. The work of reinforcement, etc., are carried out on a scaffolding device 13, and after the panels 14 and 15 are connected, concrete is laid in and on the panels 14 and 15. Accordingly, the mold frame device can be made lightweight, and workability can be improved.