Provided is a network resource provisioning method for bandwidth guarantee per flow in a differentiated service Internet in which bandwidth needed for each flow is individually requested. The method includes setting an optimum path between a source node and a destination node based on a request for traffic for a specific period of time; performing static provisioning in which bandwidth is allocated to the optimum path according to a service class thereof; determining whether all of the bandwidth allocated to the optimum path by performing static provisioning are used up, and accepting connection admission according to the determination result; and when connection admission is not accepted, performing dynamic provisioning in which additional bandwidth is allocated to the optimum path based on a request for traffic from a new incoming flow. Accordingly, it is possible to efficiently provide a quality-guaranteed service by accepting a request for bandwidth per flow.