Possible ferromagnetic and ferroelectric phases are explored for bismuth transition-metal oxides with doubleperovskite structure A2BB0O6 on the basis of first-principles calculations within the local spin-density approximation (LSDA) and generalized gradient approximation (GGA). It is found that a lattice instability of the cubic to a non-centrosymmetric phase always happens in the all cases of lead and bismuth perovskite oxides with the 3d transition-metal ions at the B site. Placing bismuth ion at the A site in the double-perovskite structure, several sets of the 3d transition-metal ions are selected according to their total valence sum and the Goodenough-Kanamori rule for the superexchange coupling. Ferromagnetic solutions are actually obtained both within LSDA and GGA for Bi2CrFeO6, Bi2MnNiO6 and Bi2CrCuO6. For non-centrosymmetric monoclinic Bi2MnNiO6, the ferromagnetic and ferroelectric phase has the spin magnetic moment of 5μB and the electric polarization of 28μC/cm2.