Method for forming coating film on internal surface of elongated tube and unit for forming the same

A method for forming a coating film on an internal surface of an elongated tube, comprising:

• longitudinally holding the elongated tube to flow therethrough a coating solution containing a solvent whose viscosity is to be reduced by heating, so that the coating solution is applied to the internal surface of the elongated tube;
• and thereafter,
• drying the coating solution applied to the internal surface of the elongated tube while carrying out a heat process for sequentially heating the elongated tube from an upper side to a lower side thereof by using a heat source,
• the heat process including:
• adjusting the descending rate of the heat source so that a through-hole in the elongated tube is clogged with the coating solution whose viscosity is reduced by heating of the heat source;
• and sucking the through-hole in the elongated tube from the lower side thereof so that a portion of the through-hole that is clogged with the coating solution moves downwards along the elongated tube.