A method of producing parboiled rice that does not require waste water treatment equipment and that enriches the amount of .gamma.-aminobutyric acid contained in the parboiled rice. The method includes partially milling raw material brown rice, wetting the partially milled rice grains by forced-air using moist air or mist, moisture-tempering the wetted rice grains, steam-boiling the water-tempered rice grains at normal pressure to heat the rice grains with steam, steam-boiling the rice grains heated in the normal pressure steam-boiling process using pressurized steam, cooling the rice grains steamed under pressure in the pressurized steam-boiling step to cool at least a surface of the rice grains, finish milling the rice grains cooled in the cooling step, and drying the finish-milled rice grains.