Abstract: For making a mattress web having two fabric webs which are attached to one another in a transverse direction of the web by seams that are spaced apart in a longitudinal direction of the, thereby to form a succession of sleeves, each of which contains a slightly tensioned spring, one of the fabric webs is continuously conveyed in the longitudinal direction in such a manner as to be supported from below. An upwardly opening curve is formed in the transverse direction. A respective spring is introduced into each curve from above, the spring being non-tensioned and having a height exceeding the curve depth. While in the curve, the spring is compressed in the vertical direction under the action of a force acting at a distance from the downstream wall of the curve, and the curve, with the compressed spring therein, is brought together with the other of the two fabric webs, which is continuously conveyed in a longitudinal direction.