A midget respirator gas tank apparatus comprising a plurality of small gas tanks each including a pin-penetrable position. The gas tanks are removably mounted in holders with the pin-penetrable position held in a gastight space. A pressure regulator is connected to the holders for communication through gas passages. A pin mechanism is supported in a gas-tight state in one of the holders for perforating one of the gas tanks at the pin-penetrable position. A piston drive pin mechanism is supported in the other holder for perforating the other gas tank under pressure of a respirable gas jetting out the gas tank perforated by the first-mentioned pin mechanism. The pressure regulator regulates the pressure of the respirable gs and supplies the pressure-regulated gas to a mouthpiece.