PURPOSE: To improve usage convenience and obtain a sufficient heat insulating effect by a method wherein, in a heat insulation bag for storing a PET bottle, a pair of movable heat insulation materials formed into a board-like shape are provided in an outer covering material formed into a bag-like shape in such a way that they can be freely taken in and out.

CONSTITUTION: A cold insulation-specific bag is composed of a bag-like part 3 and a bending cover part 5 and the bag-like part 3 is formed of a front face sheet 19 and a rear face sheet 21 each of which consists of a multilayer structure. The bending cover part 5 is formed by extending upwards the rear surface sheet 21. A pair of rectangular heat insulating materials are provided inside the bag-like part 3 in such a way that they can be freely taken in and out and a pair of easy zippers (Velcro tapes) 13a and 13b are provided in the inner surfaces of the front and rear face sheets 19 and 21 corresponding to the opening edges of the bag-like part 3. The front face sheet 19 is provided with a cut line 9 immediately above an easy zipper 11a and the neck part of the PET bottle 41 in the bag-like part 3 alone can be projected through the cut line.