A cylinder includes a cylindrical portion, an insertion portion, and a first sealing portion. The cylindrical portion has a central axis, extends in an axial direction along the central axis, and allows liquid to flow. The insertion portion extends along the central axis and is inserted into the inside of the cylindrical portion. The first sealing portion seals a space between the cylindrical portion and the insertion portion. The insertion portion includes a recessed portion and a second sealing portion. The recessed portion is annular. The recessed portion is located along an outer peripheral surface of the insertion portion and accommodates the first sealing portion. A second sealing portion seals a space between a step on a bottom surface of the recessed portion and the first sealing portion.