Providing a method for correcting a data of irregularity of a surface of a body of rotation with an eccentricity included to a data being not affected by eccentricity. The distance data Lk between the tire crown portion 10t of the tire 10t to be inspected and the distance sensor is measured at each of measurement points Xk at every angular displacement Δθ in a circumferential direction of the tire and also radius value rk are computed from the above distance data Lk and the distance LD between the center of rotation of the tire and the distance sensor; and further the surface length Sk is computed by integrating the radius value rk with respect to Δθ from the measurement starting point to a current measurement point k and the irregularity data is converted into the form of (Xk, rk) and then the radius values Rk at the irregularity computing points Xk dividing the one round surface length Sk of the tire into equal intervals are computed based on the radius values rk and rk+1 at the measurement points Xk and Xk+1 adjacent to the irregularity computing point Xk, serving as an irregularity data (Xk, Rk) at respective points dividing the surface of the tire crown portion into equal intervals circumferentially the tire.