PURPOSE: To simplify the execution by connecting an internal corner part pillar of a housing unit provided with an outer wall panel to an internal angle top part pillar, on a horizontal plate and further mounting a guide member to the pillars adjacent at a right angle to insert an internal corner outer wall panel from the upper part.

CONSTITUTION: An internal corner part pillar 1a of a housing unit A, pointing an outer wall panel 3a consisting of an ALC plate or the like, is connected to a pillar 1b of a unit B, pointing a panel 3b adjacent at a right angle, and to a pillar 1c in an internal angle top part of the third unit C by an L-shaped horizontal junction plate 6. Guide members 10a, 10b of an internal corner outer wall panel 2 are mounted to side surfaces of the pillars 1a, 1b. The internal corner outer wall panel 2 of L-shaped section, consisting of an ALC plate or the like, is inserted between the panels 3a and 3b from the upper part and fixed. In this way, the execution can be simplified.