[Problem to be Solved] To provide a resonance calculation program capable of evaluating a physical quantity such as an effective cross section in a radial direction of a circular region of a fuel rod by making a resonance calculation based on the equivalence principle.[Solution] A resonance calculation program for calculating an effective cross section by performing a resonance calculation based on an equivalence principle includes a radial-distribution calculation step S8 of calculating a distribution of the effective cross section in a radial direction of a circular region by calculating the effective cross section defined by a predetermined calculation expression including a geographical coefficient for each of a plurality of annular regions while a neutron escape probability in a resonance region is expressed by a polynomial rational expression including the geographical coefficient serving as a factor representing geographical shapes of a plurality of annular regions that are circumferentially annular and that are obtained by radially dividing the circular region that is an axial cross section of a fuel rod at predetermined intervals.