Study of the magnetic-field dependence up to 15 T of the positive magnetoresistance is made on n-type ${\mathrm{CuInSe}}_{2}$ where conduction by the variable-range-hopping mechanism of Mott type is observed below 45 K. It is shown that ln[\ensuremath{\rho}(B)/\ensuremath{\rho}(0)] is proportional, at different temperatures up to 40 K, to ${\mathit{B}}^{2}$ and ${\mathit{B}}^{1/3}$ below and above ${\mathit{B}}_{\mathit{c}}$, which separates the weak- and strong-field regimes. This confirms the theoretical prediction for the field dependence of the magnetoresistance when the conduction is by the variable-range-hopping mechanism with constant density of states at the Fermi level.