An active search method in a wireless LAN system is disclosed. The active search method comprises the steps of: transmitting, through an arbitrary channel, a preceding probe request frame for confirming the existence of an access point; acquiring, from at least one access point, a probe ACK frame that is a response to the preceding probe request frame; setting a maximum waiting time on the basis of the number of probe ACK frames; and performing an active search for an access point in the arbitrary channel for the maximum waiting time. Therefore, the waiting time for receiving a probe response frame can be reduced.