We successfully introduced high-density linear defects as artificial pinning centers (APCs) of the quantized vortices into YBCO films, during the film deposition procedure. APCs were introduced perpendicular to the film surface by using the distributed nano-sized Y2O3 islands prepared on SrTiO3(100) substrates. It is possible to induce strong changes on the shape and density of the Y2O3 islands by varying the deposition and annealing conditions. The highest Y2O 3 islands density, 226/μm2, was obtained with fifteen laser pulses at 800°C of substrate temperature, and applying an annealing temperature of 800°C. Even if only a small fraction of the induced defects act as effective pinning centers, Jc of YBCO film grown on the Y 2O3 nanoislands/SrTiO3 substrate increased to 1.8 × 107 A/cm2 (20 K, B//c, 0 T), which is 1.5 times higher than that of the pure YBCO film.