To improve mechanical properties of porous metals, formation of skin layer on the surface of porous metals is effective. Friction stir incremental forming (FSIF) and incremental hammering (IH) processes were combined to form skin surface layer on a closed-cell type aluminum foam without causing the inside fracture. The cell walls at the surface of the aluminum foam were folded by IH process in the early stage of the process, and then the folded cell walls were stirred and joined by FSIF process. The friction stirred surface layer formed by the combination of IH and FSIF processes was approximately 1.6–4.0 times thicker than that formed by FSIF process. The specific compressive strength of the aluminum foam with the friction stirred surface layer was 1.2–1.6 times higher than that without the friction stirred surface layer due to the formation of the sandwich structure. Influence of the thickness and structure of the skin surface layer on the compressive strength of the aluminum foam with the skin surface layer was discussed.