PURPOSE: To facilitate the adjustment of dimensions and uneven surface, by forming a wooden beams having grooves at the opposite faces of the longer sides and extending the wooden beams as vertical frames of both sides and fitting panels in the wooden beams to form a wall panel.

CONSTITUTION: Wooden beams 2 as vertical frames 4 of both sides, which are selected from wooden beams 2 with a rectangular section, are erected to form extended parts 41 and grooves 21 are provided respectively at the opposite faces of the longer sides thereof A panel 3 is fitted to the wooden beams 2 to form a wall panel 1. When reforming a mansion or the like, these wooden beams 2 having grooves 21 are arranged on the underlayer of a floor and a ceiling. And the extended parts 41 of the vertical frames 4 are cut so as to be lower than the height between the upper and lower wooden beams 2 and further, sliding connection members 5, 6 are fitted respectively in the upper and lower grooves 21 of the vertical frames of wall panel 1 and fixed in the grooves 21 of the wooden beams 2 arranged on the floor and the ceiling.