Abstract Lateral distributions of the critical current density ( J c) in YBCO coated conductors were measured by the magnetic knife method. It was observed that J c decreased near the edges of the coated superconductors. By considering the measured lateral distributions and the magnetic field dependence of J c, electromagnetic field analyses were performed to calculate the magnetization losses in the coated superconductors subjected to an AC transverse magnetic field. The calculated and measured magnetization losses were in good agreement. Deviations of the measured magnetization losses from the analytical values based on a uniform J c distribution can be explained by non-uniform J c distributions in actual coated superconductors. Larger loss generation mechanism in YBCO coated conductors with non-uniform J c distributions at small magnetic field was revealed by temporal evolutions of current density, magnetic flux density, and electric field in the numerical analyses.