A battery module with high impact resistance is provided. A battery module using an elastic body such as rubber for its exterior body covering a battery is provided. A bendable battery module is provided. As the exterior body covering a battery, an elastic body such as rubber is used, and the exterior body is molded in two steps. First, a first portion provided with a depression in which a battery is stored is molded using a first mold. Next, a battery is inserted into the first portion. Subsequently, second molding is performed using a second mold so as to fill an opening of the depression in the first portion, so that a second portion is formed. The second portion serves as a cover for closing the opening of the depression in the first portion. The second portion is formed in contact with part of the electrodes in the battery and part of an end portion of the second exterior body in the battery.