Fine bubble generator

A fine bubble generator that is provided in a flow channel in which a liquid flows and generates a bubble in the liquid flowing in the flow channel, comprising:

• a pair of outer members disposed in an axial direction and having a tubular shape in which the liquid flows in the axial direction, a first helical part helically extending in a circumferential direction being formed on an inner surface of the outer member;
• a pair of inner members disposed in the axial direction and arranged in the outer member with an outer surface thereof facing the inner surface of the outer member at a predetermined distance, a second helical part helically extending in the circumferential direction being formed on the outer surface of the inner member;
• and
• a middle member that is arranged between the outer member and inner member on one side in the axial direction and the outer member and inner member on another side in the axial direction, supports the inner members, and have a through-hole that allows the liquid to pass therethrough in the axial direction,
• wherein a liquid passage hole is provided that penetrates radially central parts of the inner members and the middle member from a liquid inlets side of the inner member on the one side to a liquid outlet side of the inner member on the another side in the axial direction, and
• the liquid flows between the first helical part of the outer member on the one side and the second helical part of the inner member on the one side and through the liquid passage hole, and the liquid having passed through between the outer member on the one side and the inner member on the one side passes through a through-hole in the middle member, flows between the first helical part of the outer member on the another side and the second helical part of the inner member on the another side, and is merged with the liquid having passed through the liquid passage hole on the liquid outlet side of the inner member on the another side.