FIELD: physics. SUBSTANCE: invention relates to laser engineering. Method of creating laser-active colour centres in α-Al2O3 consists in the fact that simple colour centres are oxygen vacancies captured one or two electrons (F- and F+-centres) generated during growing or as a result of thermochemical treatment of initial crystals, are converted into complex, optically active in infrared, F2+ and F22+-centres. Conversion is carried out by heat treatment at a fixed temperature in range of 800–900 °C for 1–10 minutes with simultaneous irradiation of crystal with full spectrum of mercury light source with power density in range of 10-2–1.0 W/cm2. EFFECT: technical result consists in excluding the use of radiation technologies when creating laser-active centres in crystals α-Al2O3.