PURPOSE: To improve the workability of a girder-eave ceiling in an internal angle section.

CONSTITUTION: The execution method is carried out to a girder-eave ceiling in an internal angle section, to which a wall panel 1 is disposed so as to be approximately crossed at a right angle, engaging pieces 3 are extended to support fittings 2 hung and supported to one wall panel 1 in an oblique upper section. Slipping-off preventive pieces 4 are extended to the upper sections of the engaging pieces 3. Pieces 3a for engagement are elongated to support fittings 2a hung and supported to another wall panel 1a approximately horizontally. An approximately L-shaped engaged piece 6 is mounted to an indoor side end section on one wall panel 1 side of a girder-eave ceiling material 5. The engaged piece 6 is retained to the engaging pieces 3, the girder-eave ceiling material 5 is slid and moved to another wall panel 1a side, an end section on another wall panel 1a side of the girder-eave ceiling material 5 is placed and fastened to the pieces 3a for engagement.