A cartridge manufacturing method is a method for manufacturing a cartridge having a case, a chamber adapted to filled with printing material, a supply port for leading the printing material inside the chamber to outside the case, a flexible sheet member constituting at least a portion of the chamber, and a biasing member that biases the sheet member in the direction that expands the capacity of the chamber. Pressure is made to act on the printing material, and the printing material is filled from the supply port to inside the chamber.