An optimal process determining system executes a step of calculating a temporary process that includes information of a plurality of individual processes. According to an example, each process includes a tooling including of a tool, a holder, a tool projection length, and a sequence of the plurality of individual processes. A similarity between the toolings of two individual processes is calculated. In addition, a calculation is performed relating to a plurality of integrated processes for which the tooling of one of the individual processes having a high similarity is integrated into the tooling of the other one of the individual processes. In addition, an optimal process is determined from the plurality of integrated processes on the basis of an actual machining time in each of the integrated processes, a unit integration reduction time reduced as one of the toolings of the individual processes is integrated, and the number of the individual processes integrated.