Abstract: The apparatus comprises a base having bed support structure pivotally coupled thereto for rocking motion about an upper axis. The bed support structure includes a first guide fixedly connected thereto for rocking motion with the bed support structure. A second guide is pivotally connected to the base for rocking motion about a lower axis. A drive, crank, and linkage are employed for rocking the second guide. Coupling means couples the two guides together such that the first guide and hence the bed support structure is rocked about its axis as the second guide is rocked about its axis. Adjusting means adjusts the position of the coupling means relative to the two guides to adjust the angle through which the support structure may be rocked.