A supporting frame of an electric bed, which is used to be connected with a lateral board, includes a base, a supporting portion disposed on the base, and an extended supporter. At least a part of the supporting portion is movable relative to the base. The lateral board is adjacent to the edge of the supporting portion. The extended supporter has a transverse portion extended from the base toward the lateral board, and a connecting portion located at a free end of the transverse portion. The transverse portion and the supporting portion have a distance therebetween. The connecting portion is used to be connected with the lateral board, so that the lateral board of the bed frame is fixed by being connected with the base by the extended supporter, and the user is prevented from being pinched.
