PURPOSE: To assemble and fix a prefabricated furniture efficiently and sturdily by inserting both wing pieces of a corner joint into the hollows of a post, pressure-fitting a fixing pin to fix at specified height and position, and inserting and fixing enclosing frame members on No.1 and No.2 block pieces.

CONSTITUTION: Both wing pieces 33 of a corner joint J are inserted into the hollows of a post P. The shaft leg part 39 of a fixing pin W is pressure-fit from the upward into the pin socket O till its head 40 abuts, and the corner joint J is fixed at the specified height position of the post P making use of the flexible deformation of both wing pieces 33. Next, enclosing frame pieces F1, F2 are inserted and fit into No.1 and No.2 block pieces 30, 31 of the corner joint J, and an engaging projection 26 is fitted into the engaging recess 34 of the block piece 30 to assemble and fix. A corner part of metallic enclosing frame members can be efficiently and studily assembled and fixed this way.