An excimer laser generating system includes a laser chamber (1) whose inner surface (101) is covered with a fluorine-passivated surface. Preferably, the surfaces (102,103) of a blower (23) and heat exchanger (24) disposed in the laser chamber(1) are also covered with a fluorine-passivated surface. The fluorine-passivated surface (101,102,103) may be formed of a wide variety of materials including an aluminum oxide film, a fluoride film containing aluminum fluoride and magnesium fluoride, iron fluoride, and nickel fluoride. Preferably, the excimer laser generation system includes a gas supply system having an inert gas purging system so that gas sources can be replaced without exposing the inside of gas supply pipes to atmosphere. With the above arrangement, the excimer laser generating system can generate a laser beam pulse whose energy and shape are maintained constant for a long period of operation time without encountering serious degradation. The invention also provides a high-reliability step-and-repeat exposure apparatus using the above excimer laser generating system, capable of exposing a very fine pattern.