This method comprises: comparing a calculated value of a jumping torque (Tq) obtained by substituting various parameter values of the product (ES) of a longitudinal modulus (E) and the cross-sectional area (S) of a toothed belt (1), a tooth height (h), a pulley pitch diameter (Rr), a pulley pitch diameter (Rn), an initial tension (T0), a tight-side span length (Lt), a slack-side span length (Ls), a wrap angle (θr), and a wrap angle (θn), into an expression (1)- an expression (3) and an actually measured value of the jumping torque (Tq) to each other; storing, in a storage unit (12), the value of an overall correction coefficient (K) and the value of a mesh correction coefficient (Kmn) of a driven pulley, each of which is determined in advance as a value that minimizes the average value of the difference between the compared values; and substituting the stored various parameter values, the value of the overall correction coefficient (K), and the value of the mesh correction coefficient (Kmn) into the expression (1)- the expression (3) to calculate the jumping torque (Tq) of the toothed belt (1) wound around a driving pulley (DR) and the driven pulley (DN).