This paper treats weight distributions of the coset leaders of binary linear block codes. We first present a method for computing the weight distribution of the coset leaders of a given code using two tables each of which stores the weights of the coset leaders of a related code of the code. Then, the weight distributions of the coset leaders of the (N,K) Reed-Muller codes, binary primitive BCH codes, and their extended codes with N 128 and 29 N-K 42 that are obtained by using the computing method are given.