The method for performing a random access procedure by a user equipment in a network in which a plurality of communication systems interwork may comprise: establishing an association with an access point (AP) of a neighboring wireless LAN communication system if it is impossible to perform a direct uplink transmission to a cellular communication system of the plurality of communication systems or that the UE is located in an area where direct uplink transmission is not possible; transmitting, to the AP, a first message including a random access preamble sequence; receiving a second message from a eNode B of the cellular communication system in response to the first message; transmitting, to the AP, a third message including the received second message and a radio resource control (RRC) connection request; and receiving, from the eNode B, a fourth message related to an RRC connection setup in response to the third message.