Thin films of Y‐Ba‐Cu‐O wereinsituprepared with the use of a simple conventional inexpensive vacuum system. No thickness monitor or control system is required. A pulverized mixture of Y, BaF2, and Cu constituents weighed in the atomic proportion was evaporated from resistively heated source onto a MgO substrate. The substrates temperature was then raised to 700 °C after evaporation. Oxygen was injected through a nozzle placed near the substrate surface, thus raising the pressure to about 8 Pa (60 mTorr). The film was kept at this stage for about 15 min, after which it was gradually cooled to room temperature and the pressure raised to atmospheric pressure. The obtained films with no further heat treatment were found to be superconductors with zero resistance at 85 K detected by four‐probe dc measurements.