To provide a chair which requires neither high technical capabilities nor efforts in assembling work.

A seat plate 3 is arranged in right and left seat reception side frames 25. The seat reception side frames 25 include inclination parts 253, 254 which are formed to gradually change horizontal distances from the front end sides to the rear end sides. The seat plate 3 includes projections which are arranged to meet the inclination parts 253, 254 of the seat reception side frames 25.