To provide an arrangement structure of a seat belt device for a vehicle capable of securing a component mounting space of vehicle body constituting parts on both vehicle body sides, while unnecessitating improvement of strength of a seat device when mounting the seat belt device.

In this arrangement structure, a retractor device 73 is provided to take up a seat belt 71 for constraining an occupant sitting on a rear seat 3 to be drawable, corresponding to the rear seat 3 provided with the seat cushion 31 forming a seat surface and a seat back 32 provided in a rear part of the seat cushion 31. On a rear side of the rear seat 3, a cargo chamber L capable of mounting articles is formed. The cargo chamber L is provided with a tonneau cover case 4 which is separated from the rear seat 3, extends at a position of a prescribed height or more from a cargo chamber floor 1b in a vehicle width direction toward both trims 5 of the cargo chamber L and supports the retractor device 73.