A vehicle seat suitable for weight reduction is provided. A left and right side frames 11 constituting a cushion frame unit 10 are constituted of plate-shaped frames 111, 112 which are long in a forward and backward direction and formed of a thin material made of metal with a predetermined thickness or less, a plurality of beams 121 to 125 are bridged across the side frames 11, and moreover, one or both of the side frames 11 is or are supported on a seat slide device 40 via a truss support part. In other words, the side frames 11 disposed in a direction substantially orthogonal to the plurality of beams 121 to 125 serve the role of stringers, and as a result, rigidity in the forward and backward direction of the side frames 11 in particular is high rigidity of a predetermined value or more even if they are made of a thin material, and they can be reduced in weight.