A numerical controller generates a machine configuration table in which function modules to be enabled are set based on an option or a parameter, a memory management table for managing a memory usage, and a performance management table for managing a CPU use rate. The numerical controller determines selected numbers of the function modules, based on the machine configuration table, memory management table, and performance management table, generates a module selection table, and attaches and detaches the function modules according to the selected numbers of the function modules. In this way, resources are assigned to a plurality of function modules.