A circuit analysis method of a line-to-ground voltage of a solar panel when a structure for a solar panel is struck by a lightning is discussed in this paper. The transient voltage is influenced by the current distribution within the structure. A characteristic of a voltage of an output terminal of a solar panel to ground caused by a lightning is also investigated in this paper. The resonant frequency and the maximum voltage of the overvoltage are clarified. The resonant frequency is determined by inductances of the structure, a capacitance between a frame and an output terminal of a solar panel, and a stray capacitance of a solar panel. An oscillation determined by the length of the struck structure is superimposed in the case of an indirect lightning. The characteristic of the maximum induced voltage depends on the electromotive force generated by the magnetic flux which links with a frame of a solar panel. An overvoltage caused by an indirect lightning can be obtained by an equivalent circuit with mutual impedances between a struck structure and a structure for a solar panel. The calculation can be easily carried out by the Electro-Magnetic Transients Program.