To form a room space with a high ceiling and obtain a free floor plan without restriction of arrangement of columns and beams by exposing wooden columns and beams in the room space, in a wooden prefabricated house.

A column 2 and a beam 3 forming a part of a structural body are exposed in a room 6 partitioned by an internal wall 4 and a ceiling board 5, in the second floor of a two-story wooden prefabricated house to form the room 6. The column 2 and the beam 3 are made of wood and a lustering treatment displaying curly grains is applied on the surface and the floor 7 is made of flooring fitted to the color tone of the column 2 and the beam 3. The column 2 and the beam 3 may be decorated with cloth, paint, etc. and only the column and beam may be exposed in accordance with a floor plan. In this way, the room 6 is made to be an open space with a high ceiling and a free floor plan can be obtained without restriction of arrangement of the column and the beam. And the column and the beam form accents in the room 6 and hence, a room space with individuality can be actualized.