Abstract: The degree of wear of a tire is estimated with constant accuracy. An acceleration sensor (11) is installed on the inner surface in the inner liner region of a tire to detect the acceleration of the tread in the radial direction of the tire. The peak level on the leading edge side or the trailing edge side of the tread appearing in the differentiated waveform of the detected acceleration is calculated and used as an index V of deformation speed of the tread. The degree of wear of the tire is estimated on the basis of the calculated index V of deformation speed and an M-V map (16B) showing a predetermined relationship between the degree M of tire wear and the index V of deformation speed.