A method of manufacturing a nonaqueous secondary battery, the method comprising: constructing a battery assembly with a positive electrode comprising a positive electrode active material including a layered or spinel type lithium composite metal oxide, a negative electrode comprising a negative electrode active material including a carbon material, and a nonaqueous electrolytic solution, the nonaqueous electrolytic solution containing an unsaturated carbonate; after constructing the battery assembly, activating the battery assembly to decompose a portion of the unsaturated carbonate such that a percentage of the unsaturated carbonate is adjusted to be 0.5 mass% to 0.9 mass% with respect to 100 mass% of a total amount of the nonaqueous electrolytic solution; after activating the battery assembly, self-discharging the battery assembly to measure a voltage drop amount; and after self-discharging the battery assembly, determining whether internal short-circuit occurs in the battery assembly based on the voltage drop amount, wherein the activating includes conditioning in which the battery assembly is initially charged, and aging in which the battery assembly is kept in a temperature environment of 40°C or higher and the voltage between the positive and negative electrodes is retained at 3.8 to 4.2 V, and the aging includes adjusting the percentage of the unsaturated carbonate in the nonaqueous electrolytic solution by controlling a time to keep the battery assembly in the temperature environment. constructing a battery assembly with a positive electrode comprising a positive electrode active material including a layered or spinel type lithium composite metal oxide, a negative electrode comprising a negative electrode active material including a carbon material, and a nonaqueous electrolytic solution, the nonaqueous electrolytic solution containing an unsaturated carbonate; after constructing the battery assembly, activating the battery assembly to decompose a portion of the unsaturated carbonate such that a percentage of the unsaturated carbonate is adjusted to be 0.5 mass% to 0.9 mass% with respect to 100 mass% of a total amount of the nonaqueous electrolytic solution; after activating the battery assembly, self-discharging the battery assembly to measure a voltage drop amount; and after self-discharging the battery assembly, determining whether internal short-circuit occurs in the battery assembly based on the voltage drop amount, wherein the activating includes conditioning in which the battery assembly is initially charged, and aging in which the battery assembly is kept in a temperature environment of 40°C or higher and the voltage between the positive and negative electrodes is retained at 3.8 to 4.2 V, and conditioning in which the battery assembly is initially charged, and aging in which the battery assembly is kept in a temperature environment of 40°C or higher and the voltage between the positive and negative electrodes is retained at 3.8 to 4.2 V, and the aging includes adjusting the percentage of the unsaturated carbonate in the nonaqueous electrolytic solution by controlling a time to keep the battery assembly in the temperature environment.