PURPOSE: To relax a high vacuum drawing condition and the pressure difference between mutually adjacent outlet seal parts, to stably ensure a high vacuum degree necessary at the time of tube expansion molding and to prevent the penetration of water into a tube expansion molding pipe to stably perform tube expansion molding in the production of a heat-shrinkable tube.

CONSTITUTION: A tube expansion molding pipe 10, the high vacuum drawing chamber 7 formed to the outer periphery of the inlet part of the pipe 10, the cooling chamber 9 formed to the outer periphery of the central part of the pipe 10, the low vacuum drawing pressure reducing chamber 8 formed to the outer periphery of the outlet part of the pipe 10 and the outlet seal means provided to the outlet end of the pipe 10 are provided. The tube expansion molding pipe 10 has a through-hole 10a within the vacuum chamber 7 so as to allow the interior of the pipe to communicate with the interior of the chamber 7 and has a separation part 10b within the pressure reducing chamber 8. Therefore, a heat-shrinkable tube enters a low vacuum degree condition in succession to a high vacuum drawing condition before advancing to the atmosphere.