US Patent 11904744 Vehicle-mounted seat device

A vehicle-mounted seat device includes an SB main frame, a back rest which the back of a seated person leans on, a relay disc fixed to the back rest, a first engagement member fixed with respect to the SB main frame at a position higher than the relay disc, an upper wire for suspending and holding the back rest from the first engagement member so as to be able to swing with respect to the SB main frame with the relay disc being the center, and a height adjustment mechanism constructed to be capable of pulling in part of the upper wire, so that an amount by which the upper wire is pulled in is changed to cause a change in disposed height of the back rest with respect to the SB main frame.