The magnetic and dielectric properties of ceramic composites, in which 10 mol% antiferromagnetic LaMnO3 was added to ferroelectric BaTiO3, have been investigated. X-ray diffraction measurement showed that ceramics sintered in the range of 1050-1150 degrees C are composites containing a small amount of (La, Ba)MnO3 phase along with BaTiO3 phase. These composites were found to be multiferroic materials simultaneously exhibiting ferromagnetic and ferroelectric properties at room temperature. When an electric field of 2.3 kV/mm was applied to the composite sintered at 1200 degrees C, a reduction of spontaneous magnetization as large as 70% was observed at room temperature. This reduction may be ascribed to the decrease of electron transfer interaction of the precipitated ferromagnetic (La, Ba)MnO3 caused by electrostriction of the surrounding BaTiO3 matrix.