Abstract Magnetoresistance of a strongly correlated material, La 1−xCa xMnO z film was investigated. Films were fabricated on MgO(100) single crystal substrates by an ion beams sputtering method. A giant and isotropic magnetoresistance effect was observed for which the maximum was as huge as −53 %. The maximum value was obtained at the critical temperature of the M-I (metal-insulator) transition. By consideration of the spin dynamics together with temperature dependency of magnetoresistance, the magnetoresistance effect was attributed to spin-dependent electron scattering due to fluctuation of the spin canting angle.