A slurry containing YBa2Cu3O7−x particles and a fine YBa2Cu3(OH)x colloid solution was prepared, and a large‐scale bulk YBa2Cu3O7−x superconductor (about 50 mm × 35 mm × 2 mm) was produced by plastic forming without high‐pressure molding. The samples molded from the slurry were dried and then fired at 1223 K in air. X‐ray diffraction data indicated that the samples had the characteristic orthorhombic YBa2Cu3O7−x structure. Measurements of electrical resistance were carried out between 300 and 50 K by the standard four‐probe DC electrical measurement. The samples began superconducting at an onset temperature around 92 K, and the full‐transition temperature (critical temperature) (Tc) was 88.7±1.4 K. The critical current density (Jc) measured at 77 K was about 440 A/cm2, the value of Jc was improved by the heat treatment under an oxygen atmosphere, and Jc=1.6 × 103 A/cm2 was observed. Under the magnetic field (B=1 T), the sample held its superconductivity, and demonstrated that this method can be used to produce the magnetic shielding used in magnetic resonance imaging diagnosis.