Abstract: An apparatus is used to form a container from a blank which has innermost fold lines that confine a closed bottom of the container, and outer fold lines that extend outwardly from four corners of the bottom. The apparatus includes a blank forming device which defines a forming passage of polygonal cross-section and having four corners. A blank feeding device is adapted to feed the blank towards the blank forming device in a first direction substantially parallel to the cross-section of the forming passage. A punching mechanism has a punch head of polygonal cross-section and capable of passing through the forming passage in a second direction transverse to the first direction. The punch head has a forward end formed with a polygonal push pad for pushing the blank through the forming passage.