Abstract: An internal pressure inspection is simply conducted for cans of types different in dimension and for assuredly removing defective cans. The inspection apparatus comprises first and second can barrel pressure detectors and a can cover pressure detector for detecting the internal pressure of a can, and a can sensor for sensing a can, which underwent the detection of the internal pressure, to output a can sense signal. In the inspection apparatus, a control unit decides the acceptance or failure in the can internal pressure and, when the failure decision is made, starts a defective can removal unit on the basis of the can sense signal from the can sensor. An apparatus body has a separation change mechanism including a width variable gauge which is placed between first and second movable frames and which can change its own width in accordance with its own rotation. The first and second movable frames and which can change its own width in accordance with its own rotation.