To provide a novel structure of a separator in a secondary battery. A nonaquesous secondary battery includes a positive electrode, a negative electrode, an electrolyte solution, a first separator, and a second separator. The first separator and the second separator are provided between the positive electrode and the negative electrode. The first separator is provided with a first pore, the second separator is provided with a second pore, and the size of the first pore is different from the size of the second pore. Furthermore, the proportion of the volume of the first pores in the first separator is different from the proportion of the volume of the second pores in the second separator.