PURPOSE: To obtain the titled container which is so thin at the mouth to tighten it by winding and hard to crack due to vertical array and hence facilitates the setting in a vending machine by a thermal molding employing a split die of a low heat conductivity with the inner diameter smaller than the diameter of the mouth of a female force.

CONSTITUTION: A thermoplastic resin sheet 11 is heated and grasped with a ring-shaped clamp 4 and a clamp section 16. Then, a plug 3 with the diameter 0.6W0.8 times larger than that of the mouth of a female force pierces a split due 7 with the inner diameter 0.8W0.95 times larger than the diameter of the mouth 13 of the female force and further sticks out into the space 6 of the female force. Then, air between the female force 5 and the sheet 11 is discharged from a path 12 and a pressure fluid is forced into the space 6 from a path 10 to mold a container. The plug 3 and an upper clamp 4 are lifted to open the split die 7 to take out the container.