A method of testing a secondary battery including: a positive electrode current collector; a positive electrode active material layer retained on the positive electrode current collector; a negative electrode current collector; and a negative electrode active material layer retained on the negative electrode current collector and disposed so as to oppose the positive electrode active material layer, the negative electrode active material layer being wider than the positive electrode active material layer and disposed so as to cover the positive electrode active material layer, the method comprising: step A of charging the secondary battery to a predetermined charge voltage; step B of setting aside the secondary battery for a predetermined time after the step A; step C of discharging the secondary battery to a predetermined discharge voltage after the step B; step D of detecting a battery voltage increase for a preset time after a predetermined time has elapsed after the step C; and step E of performing a pass-or-fail determination about a measurement of how much the negative electrode active material layer of the secondary battery covers the positive electrode active material layer, by providing a threshold value of the battery voltage increase obtained in the step D, wherein, in the step E, the threshold value is determined based on a relationship between secondary batteries each of whose measurement of how much the negative electrode active material layer covers the positive electrode active material layer is known and the battery voltage increase detected in the step D for each of the secondary batteries. a positive electrode current collector; a positive electrode active material layer retained on the positive electrode current collector; a negative electrode current collector; and a negative electrode active material layer retained on the negative electrode current collector and disposed so as to oppose the positive electrode active material layer, the negative electrode active material layer being wider than the positive electrode active material layer and disposed so as to cover the positive electrode active material layer, the method comprising: step A of charging the secondary battery to a predetermined charge voltage; step B of setting aside the secondary battery for a predetermined time after the step A; step C of discharging the secondary battery to a predetermined discharge voltage after the step B; step D of detecting a battery voltage increase for a preset time after a predetermined time has elapsed after the step C; and step E of performing a pass-or-fail determination about a measurement of how much the negative electrode active material layer of the secondary battery covers the positive electrode active material layer, by providing a threshold value of the battery voltage increase obtained in the step D, wherein, in the step E, the threshold value is determined based on a relationship between secondary batteries each of whose measurement of how much the negative electrode active material layer covers the positive electrode active material layer is known and the battery voltage increase detected in the step D for each of the secondary batteries. step A of charging the secondary battery to a predetermined charge voltage; step B of setting aside the secondary battery for a predetermined time after the step A; step C of discharging the secondary battery to a predetermined discharge voltage after the step B; step D of detecting a battery voltage increase for a preset time after a predetermined time has elapsed after the step C; and step E of performing a pass-or-fail determination about a measurement of how much the negative electrode active material layer of the secondary battery covers the positive electrode active material layer, by providing a threshold value of the battery voltage increase obtained in the step D, wherein, in the step E, the threshold value is determined based on a relationship between secondary batteries each of whose measurement of how much the negative electrode active material layer covers the positive electrode active material layer is known and the battery voltage increase detected in the step D for each of the secondary batteries.