Provided is a method for transmitting a random access preamble by a user equipment (UE) in a wireless communication system supporting a narrow band-Internet of things (NB-IoT). Specifically, the UE transmits the random access preamble to an eNB in a subcarrier allocated by the eNB according to a specific preamble structure and receives a random access response message from the eNB in response to the random access preamble. In this case, the random access preamble is repeatedly transmitted 16 times during a predetermined duration and then, a gap is inserted for a predetermined time and the predetermined duration is determined by multiplying a transmission duration in which the random access preamble is transmitted by the number of repeated transmission times.