<p>A seat according to this invention comprises a seat part and a backrest (12) attached to a rear side of the seat part (11). The seat part comprises a cushion attached to a pair of side supporting frame members connected with each other. The backrest comprises a cushion attached to an inverse U shaped back frame (60). Each end of the inverse U shaped back frame (60) is connected to each rear end of the side supporting frame members of the seat part. The inverse U shaped back frame comprises side supporting parts that are positioned in parallel and a top supporting part that connects top ends of the side supporting parts. Lower ends of side supporting parts are connected to rear ends of the side supporting frame members of the seat part via lower attaching parts, respectively. Each lower attaching part has an ear part that projects frontward. Supporting members connect between the side supporting parts and the ear parts of the lower attaching parts, respectively. According to this invention, a rearward tilting of its backrest can be restrained and absorb impact energy when a rear impact acts on the seat.</p>
