NOVELTY - The apparatus (1) has a seal chamber (2) which is provided with chamber portion (6) having opening. A lid portion (7) is provided rotatably with respect to chamber portion to close the opening. A first liquid seal structure (8) seals between lid portion and chamber portion having internal space sealed from outside of seal chamber. A lid portion rotating unit rotates lid portion. A substrate holding/rotating unit holds and rotates substrate in internal space of seal chamber. A treatment liquid supplying unit supplies treatment liquid to substrate rotated by substrate holding/rotating unit.    USE - Apparatus for treating substrate such as semiconductor wafer or glass substrate for LCD, plasma display device (PDD), field emission display (FED), optical disk, magnetic disk, magneto-optical disk, photo mask, and solar cell.    ADVANTAGE - The sufficient control of the atmosphere in the treatment chamber can be achieved by sealing the internal space of the treatment chamber and reducing the internal space. The substrate can be properly treated in the seal chamber such that the volume of the internal space can be reduced. The first liquid seal structure seals between the lid portion and the chamber portion. Therefore, the internal space of the seal chamber can be maintained in a sealed state even during the rotation of the lid portion. The liquid seal structure is sealed free from emission of dust and reduction in sealability as compared with a case in which the contact seal structure is employed. Thus, the seal between the lid portion and the chamber portion can be properly maintained for a longer period of time. Since the linear driving mechanism is arranged outside the seal chamber, the volume of internal space of seal chamber can be reduced. The seal liquid applied to outer surface of nozzle arm by the liquid seal structure can be removed by the seal gas of gas seal structure. The ingress of the seal liquid in the internal space of the seal chamber can be prevented. The combinational use of the seal structure and the linear driving unit can be provided, so that the size of the passage hole can be minimized. Thus the size of the seal structure can be reduced. The internal space of the seal chamber can be reliably shielded from the outside of the seal chamber by the seal structure regardless of the movement of the nozzle arm. The interior wall region is opposed to the periphery of the substrate held by the substrate holding/rotating unit located at the liquid treatment position, so that, the treatment liquid removed from the interior wall of the seal chamber can be prevented from splashing over and adhering to the substrate holding/rotating unit during the cleaning of the interior wall of the seal chamber. Thus, the contamination of the substrate holding/rotating unit can be suppressed.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for substrate treatment method.    DESCRIPTION OF DRAWING(S) - The drawing shows a sectional view of the substrate treatment apparatus.    Substrate treatment apparatus (1)    Seal chamber (2)    Chamber portion (6)    Lid portion (7)    Liquid seal structure (8)