A tank port includes a reinforcing sheet, an inner member, and an outer member. The reinforcing sheet is attached around a through-hole on the outer peripheral surface of a cylinder. The inner member includes an inner fitting plate portion attached to the inner peripheral surface of the cylinder and an inner cylindrical portion inserted into the through-hole. The outer member includes an outer cylindrical portion attached to the outer peripheral surface of the inner cylindrical portion protruding from an opening and an outer fitting plate portion attached around the opening of the reinforcing sheet. The entire periphery of the through-hole of the cylinder is reinforced by being disposed between the inner fitting plate portion and the reinforcing sheet.