PURPOSE: To form a beautiful vessel having well-regulated configuration without generating any whitening by a method wherein a die and a punch are heated to a predetermined temperature and heated air is blown from the side of the punch into the vessel to be formed in the case of forming the vessel from synthetic resin plate material.

CONSTITUTION: The hollow die 3 is fitted into a tubular member 2 on a pedestal 1 and a peripheral groove 4, having proper width, is formed on the outer wall of the die 2 while hot-water (100W110°C) is supplied into the peripheral groove 4 through a path 5 provided on the tubular member 2 to keep the die 3 in a heated condition at all times. Another tubular member 13 is fixed to the pedestal 12 and the punch 15 is fitted loosely into the bore 14 of the tubular member 13 while a heater 16 is accommodated in the punch 15 to keep it in the temperature range of 100W110°C. The tubular member 13 is provided with an air pass 22, joined with the inside of the die 3 through a gap 17 while air (about 80°C) is blown from the side of the punch 15 toward the die 3 through the air pass 22.