A mattress (13A, 13B) can be adapted to an integrated bed (100) that includes a main bed unit (20), and a wheelchair unit (10) that is separable from the main bed unit and has a wheelchair back bottom (121) , a wheelchair hip bottom (122) and a wheelchair foot bottom (125). The mattress includes a first protrusion (132) configured to be fastened to a back-section hole (121A) in the wheelchair back bottom, a fastener configured to be fastened to the wheelchair hip bottom, and a second protrusion (134) configured to be fastened to a foot-section hole (125A) in the wheelchair foot bottom.
