A thermotherapy device worn on a joint that includes a tubular holder composed of a stretchable material and a chemical warmer held in the holder. The holder has an accommodating portion in which the chemical warmer can be placed and removed therefrom, or to which the chemical warmer can be attached. The thermotherapy device can maintain temperatures suitable for thermotherapy for a long period, remains in place despite the motion of the joint, and can hold a heat-generating member in a suitable area. The thermotherapy device is thus effective for use on joints.
