To materialize a wall connection structure without leaving marks after being removed and without damaging beauty and waterproof performance by facilitating taking-in and removing.

A connection material attaching metallic material 5 is composed of: an I-shaped member 51 bending an edge part of a superposition part 512 and forming an locking pawl 511; a fixing means 53 for superposing and fixing an L-shaped member 52 orthogonally bending an edge of a superposition part 522, forming an attaching face 523, and furthermore bending the edge and forming a locking pawl 521, and these superposition parts 512 and 522; and a receiving nut 55 held on an outer face of the attaching face 523 of the L- shaped member 52. The connection material attaching metallic material 5 is attached to a mullion 1, and a connection material 6 of the receiving nut 55 is screwed.