This article describes the numerical computation of differential equations based on the "simplest walking model," a mathematical model of walking proposed by Garcia and colleagues. The process of transforming the differential equations derived from the model into a form that can be computed numerically is presented in detail. The main readers are assumed to be those who can run the program by themselves based on information from websites, but are not familiar with the principles, and would like to improve the program by themselves and acquire applied problem─solving skills in the future. The specific program code is distributed as an appendix from the website shown at the end of the text, so those who are interested are encouraged to run the program by themselves. We hope that high school, university, and graduate students who are interested in numerical computation, as well as their supervisors, will find this paper useful as an introductory example of numerical computation.