Manufacturing method for secondary battery

A manufacturing method for a secondary battery, the secondary battery being configured to include an electrode group in a battery package, the electrode group including a positive electrode, a negative electrode, and a separator, a thickness of the separator when the separator is compressed with a pressure of 50 MPa being 70% or less of a thickness of the separator before the compression, the manufacturing method comprising:

• (a) measuring a first voltage drop amount of the secondary battery with the passage of time in a state in which a compression force in a direction crossing a lamination direction of the electrode group is applied to the electrode group via the battery package;
• (b) measuring a second voltage drop amount of the secondary battery with the passage of time in a state in which the compression force is released;
• and
• (c) detecting a small short circuit of the secondary battery by comparing the first voltage drop amount and the second voltage drop amount.