PURPOSE: To prevent the generation of a gap at the pressure contact section between a panel seal material and a vertical joint seal material when the relative positional error in the thickness direction is generated between the upper and lower wall face panels.

CONSTITUTION: The terminal section 12 of a panel seal material 4 is provided with an upward projection 14 and a downward projection 15 in addition to a straight section 13 and a taper section 9. When a relative positional error (e) in the thickness direction is generated between the upper and lower wall face panels 1, 1, the terminal section 12 is rotated, compressed, and deformed according to the change of the contact position of the upper wall face panel 1 against the terminal section 12. The upper and lower edge sections 9a, 9b of the taper section 9 are surely stuck to a mating vertical joint seal material 3, and the generation of a gap between them is prevented.