Disclosed herein is method and device for performing a Hybrid Automatic Repeat request (HARQ) based on polar codes in a wireless communication system. A transmitter transmits a first packet to a receiver. The transmitter receives a re-transmission request for the first packet from the receiver. The transmitter transmits a second packet to the receiver. Herein, each of the first packet and the second packet includes at least one information bit and at least one frozen bit. An information bit having a smallest mutual information corresponding to a bit channel within the first packet is re-transmitted through a first bit channel capable of transmitting at least one information bit included in the second packet. Alternatively, a new information bit is transmitted through a second bit channel capable of transmitting at least one information bit included in the second packet.