To improve test accuracy in hammering sound test of a sealed vessel contained in a carton.

With the inside pressure test method for a sealed vessel, the quality of the internal pressure is determined, based on frequency and strength of sound emitted by a bottle-shape can 1A, when impact force is given to the sealed vessel contained in a carton 2A by electromagnetic induction force from outside the carton 2A, and forcedly exciting the bottle-shape can 1A. The frequency, emitted by the bottle shape cans 1A, is finely divided at specific intervals in the testing method for sealed vessels, a maximum magnitude peak frequency is obtained from the distribution of finely divided frequency and magnitude (step S2), the average frequency is obtained from the distribution of each frequency and magnitude in a specific frequency region centered about the maximum peak frequency (step S5), and the quality of the internal pressure of the bottle shape cans 1A is determined, based on the average frequency.