A three-chamber tire comprises a tire body including a bead mounted to a rim and an interior hollow space therewithin to form a service chamber; a low-pressure chamber mounted circumferentially around the interior hollow space of the tire, said low-pressure chamber including a wall, at least part of which is flexible, to form a partitioned, closed space; a high-pressure chamber mounted, adjacent to the low-pressure chamber, circumferentially around the interior hollow space of the tire, the high-pressure chamber including a wall, at least part of which is flexible, to form a partitioned, closed space; a bulge portion mounted to the outer surface of the high-pressure chamber and normally urged, in a direction toward the rim to be pressed; and a control valve for the low-pressure chamber positioned between the service chamber and the low-pressure chamber, in communication with each other, wherein the communication therebetween is cut off when the air pressure of the low-pressure chamber reaches a predetermined pressure; a control valve for the high-pressure chamber enabling the communication between the high-pressure chamber and the low-pressure chamber to be possible depending on the decrease in the air pressure of the service chamber, while enabling the communication to be cut off when the air pressure of the high-pressure chamber reaches a predetermined pressure.