A method for forming an air chamber in a shoe sole includes disposing a film between two EVA sheet materials and hot-pressing the sheet materials so as to fuse the sheet materials together. The film prevents the sheet materials from being fused together so as to form a gap between the sheet materials. The air generated during hot-pressing and foaming process is accumulated in the gap so as to form an air chamber in the shoe sole such that the air chamber can be formed in the shoe sole without air bags and without injecting pressurized air into the shoe soles.