In a surge protection circuit in a three-phase four-wire circuit, a first three-phase three-wire surge module includes terminals respectively coupled to a first phase R, a second phase S, a third phase T, and a fifth phase E. A single-phase two-wire surge module includes terminals respectively coupled to one phase R among the first phase R, the second phase S, and the third phase T, to a fourth phase N, and to the fifth phase E. The second three-phase three-wire surge module includes terminals respectively coupled to the two phases S and T among the first phase R, the second phase S, and the third phase T, to the fourth phase N, and to the fifth phase E. The two phases S and T are not coupled to the single-phase two-wire surge module.