Abstract: A mushroom cultivation apparatus includes an air suction fan or a vacuum pump which suctions air in all or part of an incubation chamber, a budding chamber and a plurality of suppressing and growing chambers, which are required for cultivation of mushrooms, to reduce pressure in the chambers so that concentration of carbonic acid gas in a cultivation bottle in the cultivation chamber, the budding chamber and the plurality of suppressing and growing chambers is reduced to a predetermined concentration or less, preferably to a 15% concentration or less. Thus, carbonic acid gas in the cultivation bottle is forceably exhausted to adjust the concentration of carbonic acid gas in the cultivation bottle to an optimum condition.