To provide a rear part vehicle body structure of a vehicle capable of reducing a weight of a seat and improving a degree of freedom of design of the seat while protecting an occupant on the seat securely when a rear part of the vehicle collides.

A strength member 4 having a seat fixing part 10 of the seat 5 covering at least a part of an opening in a recessed part 2 and arranged above the recessed part 2 is provided on a floor panel 1 side having the recessed part 2 to prevent the move of a spare tyre 3 stored in the recessed part 2 by the strength member 4 when the rear part of the vehicle collides.