A mounting structure of a solar cell module includes a fastening for mounting the solar cell module on a lateral beam. The fastening includes a body, and a plurality of hooks formed at an end of the body. The hooks have a hook having a form bent toward one side, having an end directed downward and serving as a first hook, and a hook having a form bent away from the one side, having an end directed downward and serving as a second hook. The hooks are opposed to and engaged with a projection of a hooked and L-shaped form formed on the solar cell module.