A pneumatic tire comprises a tread portion, a pair of bead portions and a pair of sidewall portions, and at least one of the sidewall portions is provided with at least three strain sensors disposed at least three circumferentially different mounting positions, respectively. The at least three strain sensors are oriented at angles .theta. with respect to tire radial directions at the respective mounting positions. The orientation angles .theta. of at least two of the at least three strain sensors are different from one another and their difference(s) is(are) not less than 20 degrees in absolute value.