To provide a coater for forming a photosensitive film in which the atmosphere of an area where the coating work of forming the photosensitive film is done is made equal to clean air of a clean room, the atmospheric temperature is kept constant at room temperature and the humidity is controlled so that the photosensitive film can be formed by the coater, and to provide a plate making factory.

The coater for forming the photosensitive film is closed tightly in a casing equipped with a door. A clean air jetting duct and an air taking-in duct of an air purifying apparatus having an air-conditioning function are connected respectively to an air intake and an air discharging port of the casing. By the air purifying apparatus having the air-conditioning function, the atmosphere in the casing is made equal to clean air of the clean room, the air temperature in the casing is kept constant at room temperature and the humidity in the casing is controlled so that the photosensitive film can be formed by the coater. The plate making factory is provided with a handling robot, a coater for forming the photosensitive film with which a roll to be engraved can be transferred from/to the handling robot and a laser exposing apparatus in which required treatment is subjected to the roll to be engraved and a laser exposing apparatus. The above coater for forming the photosensitive film is installed as the coater of this plate making factory.