A not regular indefinite Stieltjes moment problem is studied in the generalized Stieltjes class N-k(k).The new class of the sequence s = {s(i)}(i=0)(l) is defined, which is called alpha-regular class. Regularization of the indefinite Stieltjes moment problem is obtained. The set of solutions of this problem is found in terms of the generalized Stieltjes polynomials and S-fractions with the shift alpha. (C) 2020 Elsevier Inc. All rights reserved.