Vehicle seat device

A vehicle seat device comprising:

• a seat back main frame that is in an upright position in a cabin, the seat back main frame being joined to a seat cushion via a reclining shaft;
• a seat back subframe that is swingable with respect to the seat back main frame at least about a roll axis;
• a backrest configured to support a back portion of a vehicle occupant, the backrest being installed on the seat back subframe and being swingable together with the seat back subframe;
• and
• a plurality of support members each having a front end joined to the seat back main frame and a rear end joined to the seat back subframe and having a variable joint-to-joint distance to limit rearward movement of the seat back subframe and allow movement of the seat back subframe about the roll axis,
• wherein the plurality of support members include a lower support member disposed in a lower half area of the seat back subframe and an upper support member disposed in an upper half area of the seat back subframe, and
• wherein a straight line connecting between the front end and the rear end of the lower support member is inclined with respect to a reference normal line so as to rise toward the front, the reference normal line being normal to a straight line connecting between an upper end of the seat back main frame and the reclining shaft.