1. A simulation method, comprising: acquiring, by input circuitry, a processing condition for performing predetermined processing on a processing target with use of plasma; calculating, by calculation circuitry, a solid angle corresponding to a field-of-view region through which plasma space is viewable from a respective predetermined evaluation point among a plurality of predetermined evaluation points on a surface of the processing target based on the processing condition; and calculating, by the calculation circuitry, an incident radical amount entering the respective predetermined evaluation point by a flux method with use of a function which takes a reaction probability between the solid angle and the respective predetermined evaluation point of a radical entering the respective predetermined evaluation point as an argument.