This study investigated the morphological differences of P. ostreatus grown in the artificial environmental conditions such as humidity, temperature, ventilation, and watering. Oyster mushroom, which was cultivated on artificial environmental condition, was shown to have different morphology of fruitbodies. The optimum $CO_2$ concentration for good morphology of P.ostreatus was 0.3%. But most fruitbody showed the morphologically low qualities in more than 0.5% of $CO_2$ concentration. In the humidity in excess of 80% at $13{sim}16^{circ}C$, the best morphology of P. ostreatus was investigated. The growth of fruitbodies of P. ostreatus in the ventilation system was good at the wind velocity ranging from $0.2{sim}0.5$ fpms and expouring type. In other conditions, P. ostreatus generally showed the morphology closing to malformation.