An adjusting device for a lumbar support comprises a pair of spaced guide members, an adjusting member coupled to the pair of guide members, and a drive mechanism for effecting an adjustment of the lumbar support. The adjusting member is displaceable along the pair of guide members and configured such that the lumbar support is adjusted when the adjusting member is displaced. The drive mechanism comprises a motor, which is provided on the adjusting member so as to be displaceable along the guide members jointly with the adjusting member. The motor may be coupled to a shaft having a structured exterior surface, the drive mechanism being configured to effect a relative displacement between the adjusting member and the shaft.