[Object] To provide an angular correction method with which angular skip does not occur in determining an angle between angular graduations of a dial of a rotary encoder by interpolation calculation. [Solution Means] Angular correction data are obtained by a residual curve determining step (S2) of determining a residual ri between a position computed from a model and an actually read position Pi, and of fitting the residual ri to a polynomial f(x) which is a function of an angular graduation image number x to determine a residual curve, r=f(x), a slope computing step (S4) of computing a tangential slope f′(xi) of the residual curve; an angular skip computing step (S5) of computing an angular graduation image position correction quantity Ci from a residual ri and the slope f′(xi), of determining a measured angle value θ0 by using the correction quantity Ci, of switching the combination of angular graduation images to a forward side and a backward side to determine measured angle values θ−1 and θ+1, and of computing the angular skip quantity; an order determining step (S7) of determining the order of the polynomial f(x) such that the angular skip quantity is minimized; and an angular correction data recording step (S8) of recording the residual and the tangential slope.