It is an object of the present invention to provide: a modified perovskite-type composite oxide, which effectively suppresses elution of A-site metals from a perovskite-type composite oxide, and which can be particularly preferably used as an inorganic filler for a composite dielectric body; a method for producing the same; and a composite dielectric material using the same. The modified perovskite-type composite oxide of the present invention is produced by primarily coating the particle surface of a perovskite-type composite oxide with silica and then secondarily coating it with a coupling agent, characterized in that the layer primarily coated with silica is produced by performing a heat treatment at 800° C. to 1200° C. on hydrolyzed silica obtained by the hydrolysis of tetraalkoxysilane.