The present invention relates to a method and a device for performing group communication based on a proximity service (ProSe) in a wireless communication system. More specifically, the method comprises the steps of: enabling a relay terminal (relay user equipment, relay UE, ProSe UE-to-Network relay) to register group communication in a network node; and enabling the relay terminal to perform the group communication with the network node, wherein the group communication is configured to transmit a downlink signal using a multimedia broadcast and multimedia service (MBMS) if the number of terminals, except for a relayed terminal (relayed user equipment, relayed UE) among a plurality of terminals registered in the network node, is not less than a reference value.