Suggested are a method and an apparatus for transmitting and receiving packets in a wireless LAN system. More specifically, an access point (AP) broadcasts a beacon frame comprising allocation information for a contention free period (CFP) and a contention period (CP) to a plurality of stations (STA). The AP receives an uplink (UL) packet from a first STA among the plurality of STAs. The AP transmits a downlink (DL) packet to a second STA among the plurality of STAs. The length of the CFP is determined on the basis of the number of first STAs and the access category of traffic for the first STA. UL packets are received in as many as the maximum number that can be transmitted within the determined length of the CFP. DL packets are transmitted in as many as the maximum number that can be transmitted during the CP.