An internal pressure inspection apparatus for a sealed container having a can lid that is attached to any of an upper end and a lower end of a can trunk, and that is deformed by an internal pressure of the container. A laser sensor adapted to measure a distance from the can lid by irradiating the can lid is situated parallel to the can lid while being allowed to move relatively with the can lid. The inspection apparatus integrates relative displacement values between a reference point closer to a center of the can lid than a seamed portion and other points closer to a center of the can lid than the reference point, and acceptability of the internal pressure is judged based on the value of integration.