Hollow fiber membrane module

A hollow fiber membrane module comprising:

• an inner case that is a member with a tubular shape;
• an outer case that is a member with a tubular shape covering the inner case from an outer periphery side with a space left therebetween;
• and
• a plurality of hollow fiber membranes that are provided in the space between the inner case and the outer case, wherein
• the inner case includes an introduction portion that is a part establishing communication between inside of the inner case and outside of the inner case on a side of one end in an extending direction of the inner case and the outer case,
• the outer case includes a discharge portion that is a part establishing communication between inside of the outer case and outside of the outer case on a side of another end in the extending direction,
• the inner case includes a bypass portion that is a part establishing communication between the inside of the inner case and the outside of the inner case on the side of the another end in the extending direction,
• the bypass portion includes at least one opening that penetrates through the inner case between the inside and the outside, and
• wherein the inner case includes one end portion with a tubular shape that is a part on the side of the one end and another end portion with a tubular shape that is a part on the side of the another end and connects to the one end portion on the side of the another end,
• the introduction portion is provided at the one end portion,
• the bypass portion is provided at the another end portion,
• the one end portion has a diameter reduced as progress from the side of the one end toward the side of the another end in the extending direction, and
• the another end portion extends along the extending direction.