A plurality of solar batteries are provided between a first substrate and a second substrate. The first substrate and the second substrate are formed of, for example, a paper or a non-woven cloth, which is a material including a natural fiber, cellulose, as the main component. Papers and silicon have relatively small difference in coefficient of thermal expansion so that warp caused by changes in the temperature is suppressed. Also, papers are light, easy to be processed and spontaneously decomposed so that disposing becomes easy. The first substrate is preferable to be transparent or semitransparent and preferable to be formed of cellophane paper, glassine paper, parchment paper, or Japanese paper. Oil may be included in the material. The second substrate is preferable to be opaque. A waterproof film may be formed on the first substrate and the second substrate.