This specification provides a method for performing early data transmission in a random access procedure in a wireless communication system.More specifically, the method performed by a user equipment (UE) includes: receiving, from a base station, a control message including first information indicating whether selection for a second transport size (TBS) smaller than a first TBS for message 3 is permitted and second information for the first TBS; transmitting, to the base station, a request for the EDT by using message 1; receiving, from the base station, message 2 including a UL grant for the message 3; determining a repetition number for the message 3 based on the control message and the UL grant; and transmitting the message 3 to the base station by the repetition number.Therefore, there is an effect that battery consumption of the UE can be reduced.