Seatback lock device and vehicle seat

A seatback lock device comprising:

• a lock main body that is attached to a side portion of a frame of a seatback coupled so as to be able to tilt forward with respect to a floor section of a vehicle body and that engages with a striker provided at a side portion of the vehicle body;
• a release lever that is coupled to the lock main body and arranged at a seat width direction inner side with respect to the lock main body, that releases engagement between the lock main body and the striker by being displaced toward a seat upper side, and that includes a strap coupling portion extending diagonally toward the seat width direction inner side and the seat upper side;
• and
• a strap having a one-end portion that is coupled so as to be able to rotate with respect to the strap coupling portion and an other-end side arranged along a height direction of the seatback due to the strap being folded at an obtuse angle at an intermediate portion of the strap, with the other-end portion inserted through a strap pull-out opening formed in a shoulder of the seatback.