To achieve sufficiently higher safety so as to cause no injury of a user or the like attributed to such a sudden movement as forward falling of an inclined member by regulating the movement more than necessary for a rear board or the like in a bed having the mobile rear board or the like.

The bed 10 has a frame 12 and a floor board member 14 supported on the frame 12 and the floor board member 14 comprises a fixed waist part board 16 fixed on the frame 12 and the freely inclinable mobile rear board 18 and a thigh board 20 and a lower thigh board 22. The bed 10 is provided with an erection regulation means 32 for regulating the displacement of the rear board 18 or the like in the direction of its erection. The erection regulation means 32 comprises a spring 34 with both ends fixed on the rear board 18 and the frame 12 and a string-like member 36 for regulating the stretch of the spring 34.