A data retransmission method for a polar code, and a device therefor are disclosed. The data retransmission method of the disclosure can comprise the steps of: generating a first data block by allocating a plurality of data bits to input bits, with high priorities, among input bits of a polar code encoding module on the basis of a target encoding rate; transmitting the generated first data block; generating a second data block by allocating first data bits among the plurality of data bits to input bits, with low priorities, among the input bits of the polar code encoding module, on the basis of the target encoding rate and shortening bits; and transmitting the generated second data block as a retransmission of the first data block.