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We have investigated the relationship between the microstructures and pinning forces by measuring the magnetic-field dependence and angular dependence of Jc in several kinds of YBCO thin films having different microstructures. A high-Jc value was kept even when the magnetic field was applied perpendicular to the film plane in the case of a c-axis-oriented film which was studded with a-axis-oriented grains. The boundaries between the a-axis-oriented grain and the c-axis-oriented grain are considered to be effective as pinning centers.