Seat back structure of vehicle seat

A seat back structure of vehicle seat, in which the seat back has one side to supportively receive a back of an occupant on the vehicle seat and another side opposite to said one side, comprising:

• an elastic back support means provided in said one side of said seat back, said elastic back support means being adapted for resiliently supporting the back of said occupant;
• a back board means provided in said another side of said seat back, said back board means having:
• one side facing to said one side of said seat back;
• and another side facing to said another side of said seat back;
• a movable connection means for connecting said elastic back support means and said back board means with said seat back so as to allow displacement of the back board means in a direction from a home position to one of said one and another sides of said seat back, while allowing the elastic back support means to be resiliently warped in a direction to said one of said one and another sides of said seat back;
• a stopper means for preventing movement of said back board means from said home position toward said one side of said seat back, and
• a biasing means for normally biasing said back board means to said home position;
• wherein said back board means is retained by said stopper means at said home position, thereby withstanding a first load applied to said another side of the back board means and allowing the back board means to be usable as a means for carrying load and cargo thereon, and wherein, by contrast, when a second load is applied in a direction to said one side of the seat back, said elastic back support means is resiliently warped toward said one side of said back board means, which in turn causes the back board means to displace toward said another side of said seat back against a biasing force of said biasing means, so that both said elastic back support means and said back board means are resiliently displaced toward said another side of said seat back.