Provided herein are a cartridge in which a pipe can be retained without increasing the number of components or suppressing pushing-out of a content and a method of designing the cartridge. A length L over which the outer peripheral surface of a pipe 36 and the inner peripheral surface of a through hole 38 contact each other when the pipe 36 is press-fitted into the through hole 38, an average outside diameter R of the pipe 36 in the range of the length L over which the pipe 36 is press-fitted into the through hole 38, and an average inside diameter N of the through hole 38 in the range of the length L are determined to meet: L×R×πx(1 - N/R)×3.3 ≥ W and 0.01 < (1 - N/R) < 0.1, wherein the maximum pushing load of the piston 4 is defined as W and a grasping force to hold the pipe 36 as the pipe 36 is press-fitted into the through hole 38 is defined as 1 - N/R.
