In a neutrino-driven supernova explosion, beta-processes are responsible for the energy deposition to the stagnated shock wave. We investigate an influence of a magnetic field on beta-processes under conditions of a core-collapse supernova. For realistic magnetic fields reachable in astrophysical objects, we obtain simple analytical expressions for reaction rates of beta-processes as well as energy and momentum transferred from neutrino and antineutrinos to the matter. In numerical estimations, we use results of one-dimensional simulations of a supernova explosion. We found that, in the magnetic field with the strength $B \sim 10^{15}$ G, the quantities considered are modified by several percents only and, as a consequence, the magnetic-field effects can be safely ignored, considering neutrino interaction and propagation in a supernova matter. The work is supported by the Russian Science Foundation (Grant No. 18-72-10070). https://arxiv.org/abs/1912.12889v2 https://journals.aps.org/prd/abstract/10.1103/PhysRevD.101.083003