An apparatus for determining a route including: a collector that collects a current amount of link traffic and current link power consumption of each link; a virtual link setter that sets virtual links for each link; a link cost calculator that calculates a link cost of each virtual link based on the estimated increase in the link power consumption; a constraint condition setter that creates a constraint condition satisfying a requirement of end-to-end quality of a request flow based on change in quality of each virtual link and satisfying a requirement of end-to-end quality of an existing flow based on the change in quality of the existing flow on the virtual link; a route determinator that determines a route having a smallest sum of the link costs including a plurality of the virtual links satisfying the created constraint condition.