To provide a chair for easily executing recycle, scrapping, or the like, and simultaneously obtaining comfortable cushionability in the chair whose core main body is constituted of a foamed styrene resin.

Arm rest parts 4 made of foamed styrene resin whose average density is not lower than 60 kg/m3 are adhered to both sides of a core body 3 of an L-shaped cross section made of foamed styrene resin whose average density is a level of 15 kg/m3 to constitute a chair main body 1 so as to freely attach and detach a seat part cushion body 2 to this main body 1. Then, this body 2 is obtained by adding a compressing load to foamed styrene resin whose average density is a level of 11 kg/m3 to restore and a recessed part (d) is formed on the receiving surface 3a of the core body 3 to obtain good cushionability.