According to the present invention, a movable wall portion for forming the outer circumference of an infant accommodation space can pivot forward about a portion of a region including the lower end portion and its vicinity of the movable wall portion from a substantially erect position to the outside of the infant accommodation space. The movable wall portion can move backward from a midway position in forward movement to the final backward moving position by its own weight while abrupt backward movement is suppressed by a damper. The present invention can provide a movable wall portion attachment mechanism of an incubator which does not produce a large sound or a large vibration when closing the movable wall portion, with a small chance that wall portions such as wall portions on the incubator base side, the movable wall portion or the like will be damaged.