To retain a comfortable posture by supporting the lumbar region of a raised body to a locking state and preventing an upper half body from being deviated downward on a mattress when raising the back-region support frame in a bed frame having the reclining back-region support frame.

The back-region support frame 3 raised/reclined on the bed frame 1 by a rod body 12 vertically turned by a motor 11, is provided with arm pieces 7 and 7 turned in the front/rear direction, on both sides of the lengthwise intermediate part of the back-region support frame 3, and lumbar region pushing-up bar 8 attached between the arm pieces 7 and 7. The arm pieces 7 and 7 are operatively connected to the rising/reclining movement of the back-region support frame 3 to turn back and forth, when rising, the lumbar region pushing-up bar 8 is made to project from the back-region support frame 3, the lumbar-region support part in the mattress 16 is curvedly deformed by a projecting portion 16a and the projecting portion 16a supports the lumbar region of the body to the locking state.