Abstract: In a tube whose internal space is partitioned by a partition wall to formed an air chamber filled with air and a sealant chamber filled with a sealant, the ratio R (R=B/A) of the length B of an outer circumference of the tube accommodated in the tire and expanded by filling of air to the length A of an outer circumference of the tube in an unexpanded is set in a range of 100% to 110%. Thus, the tension of the partition wall at the time when the tube has been expanded is suppressed to a small extent. Even if the partition wall of the tube gets a punctured wound, the partition wall having only a small tension applied thereto has a weak tendency to be intended to be contracted toward the air chamber. Therefore, little, if any, of the air in the air chamber flows into the sealant chamber and thus, a reduction in sealing performance of the sealant due to the mixture with the air is prevented.