The invention provides a backward tilting device of a vehicle seat. According to the backward tilting device of the vehicle seat, the sheet thickness of a stop sheet can be reduced, and the weight is correspondingly reduced. A hook sheet (2) is arranged on any side of a seat cushion rack (5) or a seat backrest rack (7), and a stop sheet (3) for clamping the hook sheet (2) is arranged on the other side of the seat cushion rack (5) or the seat backrest rack (7); the hook sheet (2) is formed into a trapezoidal sheet (2C) with a suspended end and protrudes towards the other side by utilizing fixation of a base end (2B) of the sheet; the stop sheet (3) is formed into the shape of a convex part (3A) with an approximately U-shaped section; each end (3B) of the convex part (3A) is fixed to a fixation object by welding, so that the stop sheet (3) is formed into the shape of a closed section; and the stop sheet (3) is clamped by the hook sheet (2), so that the tilting range of a seat backrest (SB) is limited.