Disclosed are supporting leg assemblies and foldable bed frames. A supporting leg assembly includes a lateral bar, left and right legs, and left and right supporting pieces. The left and right legs are disposed under the left and right ends of the lateral bar, respectively. The left supporting piece is in contact with left sides of the left end of the lateral bar and the upper end of the left leg, and is fixedly coupled to the lateral bar and the left leg. The right supporting piece is in contact with right sides of the right end of the lateral bar and the upper end of the right leg, and is fixedly coupled to the first lateral bar and the right leg. The left and right supporting pieces are configured to connect and support sub-frames of a fold bed frame.
