This application provides a polar code coding method, a polar code decoding method, a sending device, and a receiving device, so as to improve polar code coding/decoding performance. The method includes: selecting, by a sending device, K non-punctured-position sequence numbers as a reference sequence number set based on a quantity K of information bits and a reliability-based order of N polarized channels of a polar code whose code length is N, where a reliability of a polarized channel corresponding to any sequence number in the reference sequence number set is greater than or equal to reliabilities of polarized channels corresponding to remaining (N-K) sequence numbers, and K is greater than or equal to 1 and is an integer; determining, by the sending device, an information-bit sequence number set based on a determining condition and the reference sequence number set, where the determining condition is set based on at least one of a code rate, a mother code length of the polar code, a quantity of information bits, and a code weight; and performing, by the sending device, polar coding on to-be-coded bits based on the information-bit sequence number set.