Disclosed is a hierarchical random access method for a wireless communication system having a significantly large cell. According to the present invention, a length of a preamble sequence and a length of a reference slot may be designed based on a terminal having greatest capacity of adjusting a timing error arrived at a base station, and a slot length may be designed to be an integer multiple of the length of the reference slot depending on a timing error correction capacity, thereby enabling terminals to use various slot lengths.