PURPOSE: To secure the operation of a partition wall punching device, and simplify the mechanism of the device by providing an inclined face on the back of a punch, which is slidably inserted in a punch sliding hole, and pushing down a pressing member, which has an inclined face touching the former inclined face of the punch, at a right angle relative to the punch.

CONSTITUTION: In a device with which a cell connection hole is given on a partition wall of a mono-block container, the partition wall is inerted in a split groove 3 formed between a punch retainer plate 1 and a receiving plate 2, and a given a hole by means of a punch 4, which is slidably installed in a punch sliding hole 5. The back surface of the punch 4 is an inclined face 7, and a pressing member 8 is provided with an inclined face 9. When the pressing member 8 is pushed downward (pushed down at a right angle with the sliding hole 5), the punch 4, the inclined face 7 of which touches the inclined face 9 of the member 8, is moved forward for pressing the partition wall.