A secondary battery in which convection in an electrolyte solution occurs easily is provided. A secondary battery whose electrolyte solution can be replaced is provided. A nonaqueous secondary battery includes a positive electrode, a negative electrode, a separator, and an electrolyte solution, and the separator includes grooves capable of making convection in the electrolyte solution occur easily. The nonaqueous secondary battery has at least one expected installation direction, and the grooves in the separator are preferably formed so as to be perpendicular to an expected installation surface. The exterior body includes a first opening for injection of an inert gas into the exterior body and a second opening for expelling or injection of an electrolyte solution from or into the exterior body. An electrolyte solution replacement apparatus has a function of injecting the inert gas through the first opening and expelling or injecting the electrolyte solution through the second opening.