One embodiment of the present invention is a method whereby a network node selects a packet data network gateway (P-GW) in a wireless communication system, the method for selecting a P-GW comprising the steps of: receiving, from user equipment, an attach request including information on a group; determining whether or not the attach request is a first request from the group; and selecting a P-GW to perform a policy and charging enforcement function (PCEF) on the group including the user equipment, wherein the selected P-GW is the same P-GW selected for the group in case the attach request is a third or later request from the group.