Disclosed in the present specification is a method by which network nodes calculate an optimum path for virtualized service functions (SFs). The method can comprise the steps of: generating a service function chain (SFC), in which SFs are put in order, on the basis of subscriber information-based user policy information, session policy information, and SF state information; searching for an optimum SF set on the basis of the SFC so as to calculate an optimum service function path (SFP); and updating the SFP when any one of the subscriber information-based user policy information, session policy information, and SF state information is changed.