A signal transmitting/receiving method of a user equipment of a mobile communication system according to an embodiment of the present invention comprises the steps of: transmitting a first random access signal including a first random access preamble to a base station; receiving, from the base station, a first random access response signal including first timing advance (TA) information in response to the first random access signal; transmitting, to the base station, a second random access signal including a second random access preamble based on the state of the user equipment; receiving, from the base station, a second random access response signal including second TA information in response to the second random access signal, when the second random access signal is transmitted to the base station; and transmitting a signal to the base station according to third TA information determined on the basis of at least one of the first TA information and the second TA information. In a random access procedure for initial access to a network by the user equipment according to an embodiment of the present invention, the user equipment transmits, two or more times, an RACH preamble signal to a base station, so that a more accurate TA value can be predicted utilizing TA information from two or more response messages received.