In order to provide a lumbar support which conforms to the curve of the spinal column so as not to give a feeling of incompatibility or other unpleasant feeling, and is easily adjusted to meet a user's preference, a lumbar support 10 of the present invention is structured such that a bulging member 30 provided with two housing parts 31 and 32 to house a cushioning material for adjustment 34 is fixed on the back surface of a flexible plate 20, which is incorporated so that the front surface of the flexible plate 20 is positioned to the front surface side of a back cushion 120. Accordingly, the curvature of the two housing parts 31 and 32 does not affect a feeling of contact with the waist as it is, but works as a feeling of contact with larger curvature owing to the flexible plate 20, which results in suppression of pressure on the nervous system between the third and fourth lumbar vertebrae. Furthermore, by setting the width of a border region 33 between the two housing parts 31 and 32 in an appropriate range, it is possible to suppress a feeling of pressure on such a nervous system, and at the same time, to suppress any feeling of incompatibility or other unpleasant feeling caused by too large a curvature.