PURPOSE: To prevent a scratch and a warp from occurring by transferring a plastic film by a rolling contact in a heating step and a pressure-bonding step, and cooling a sealed sheet discharged from the sealed sheet outlet of an isolation wall, from an upper and a lower side.

CONSTITUTION: Plastic sheets 1, 1' are mounted, then are stretched over intermediate rollers 2, 2', rotary heating rollers 3, 3', pressure-bonding rollers 5, 5' and drawing rollers 9, 9' in that order, and heating elements 17, 17' and heating members 4, 4' are energized. After the lapse of a specified time, a drive motor, blowers 10, 10' and cooling fans 12, 12' are energized. Then films 1, 1' are fed out at an identical speed, and are heated to a melting temperature during their contact with the rotary heating rollers 3, 3' heated without generating a slip. Further, the films reach the pressure-bonding rollers 5, 5' preheated to a constant temperature level. On the other hand, if a realing target sheet 7 is introduced into an introduction inlet 15, it is held between the films 1, 1' and fusion-bonded between the pressure-bonding rollers 5, 5'. The sealed sheet is discharged from a sealed sheet outlet 16 in an isolation wall, then is cooled by cooling fans 12, 12' and is finally sent out by the drawing rollers 9, 9'.