Disclosed is an apparatus and a method for detecting a boundary of a frame in a wireless communication system. The apparatus includes: a controller for measuring correlation energy with preambles with respect to received signals transmitted from a transmitter, measuring strength of the received signals, and removing a sample from frames constituting the received signals, the preambles predetermined and used by the system, the sample having a ratio of the correlation energy with respect to the strength of the received signals, the ratio being smaller than a reference value; and a classifier for extracting a maximum value from the correlation energy received from the controller, and determining a boundary of a downlink of the frames constituting the received signals.