Multiferroic materials where ferromagnetism and ferroelectricity coexist are rare. We have succeeded in synthesizing new multiferroic materials Bi₂M MnO₆ (M = Ni, Co) at high pressure of 6 GPa. The crystal structures of these compounds are a heavily distorted double-perovskite (space group C2), with M ²⁺ and Mn⁴⁺ ions ordered in a rock-salt configuration. The monoclinic unit cell of Bi₂NiMnO₆ is a = 9.4630(1), b = 5.42553(8), c = 9.5352(1) Å, and β= 107.840(1)°, and that of Bi₂CoMnO₆ is a = 9.4886(2), b = 5.4444(1), c = 9.5678(2) Å, and β= 107.603(1)°. A polarized 6s² lone pair in Bi³⁺ causes the noncentrosymmetric structural distortion, which leads to ferroelectric property. On the other hand, NaCl-type ordering of M ²⁺ with e_g electrons and Mn⁴⁺ without e_g electron produces ferromagnetic exchange paths, -M ²⁺-O^2--Mn⁴⁺-, according to the Kanamori-Goodenough rules. The ferroelectric and the ferromagnetic transition temperatures of Bi₂NiMnO₆ are 455 and 140 K, respectively. The ferroelectric transition temperature of Bi₂CoMnO₆ is above 600 K, while the ferromagnetic transition temperature is 95 K.