Container manufacturing method, double container manufacturing method, double container, and method for discharging contents from double container

A method for manufacturing a double container, comprising:

• a step of producing a container main body having an inner bag and an outer shell covering the inner bag, by performing biaxial stretch blow molding on a preform having an inner preform and an outer preform disposed to cover the inner preform, wherein
• the inner preform is formed by performing direct blow molding on a molten tubular parison;
• a mouth part of the inner preform includes an engaging part for pulling out the inner bag from the container main body;
• and
• ratio of D2 to D1 is 0.35 or more, where D1 is largest outer diameter of the inner preform at the mouth part, D2 is an outer diameter of the inner preform at a height of 0.1H from a bottom part of the inner preform, and H is a total height of the inner preform.

A method for manufacturing a double container, comprising:

• a step of producing a container main body having an inner bag and an outer shell covering the inner bag, by performing biaxial stretch blow molding on a preform having an inner preform and an outer preform disposed to cover the inner preform,
• wherein
• the inner preform is formed by performing direct blow molding on a molten tubular parison;
• the inner bag includes a thin wall part with a wall thickness of 100 μm or less;
• and
• the inner preform is provided with an uneven shape or a lubricant on an outer surface of an area that includes a part corresponding to the thin wall part.