To solve problems that a screen door essential in summer is easy to collect dust and becomes rather obstructive in the other seasons; that a countermeasure against allergy, troubling increasing number of patients these years to the extent that a hay fever, in particular, is called a national disease, is a serious issue to the patients; and that a great amount of yellow sand flown from China in early spring due to global warming, desertification, etc. has an adverse effect on human health.

According to a mechanism for easily attaching and detaching all kinds of screens and nets irrespective of the mesh size, pollen and yellow sand are prevented from entering a room by stretching an anti-pollen net having fine mesh in spring and autumn when the pollen flies, and an anti-insect net having comparatively coarse mesh and good ventilating performance replaces the anti-pollen net in summer when insects become active. Thus, the screen door is utilized for a long period from late winter to late autumn, and a comfortable living space is provided in accordance with seasons.