An encoding method on the basis of a polar code in order to support an HARQ according to the present embodiment comprises the steps of: configuring, an input vector for retransmission, which has a length of N and is applied to a mother matrix predetermined on the basis of a polar code, by a wireless device, wherein the input vector is defined on the basis of a first index set for an optimized position of an information bit having a length of K, a second index set for a position of a bit to be punctured among encoded bits generated on the basis of the mother matrix, and a third index set for a position of at least one unknown frozen bit associated with an information copying scheme; and performing encoding on the basis of the input vector and the mother matrix, by the wireless device.