A laser device for an exposure apparatus may include: a MOPA-type or MOPO-type laser device including a seed laser and at least one gas discharge-pumped amplifier stage that receives output light from the seed laser as an input, amplifies the light, and outputs the amplified light; and at least one of a laser gas control device that at least changes the total pressure of a laser gas in said amplifier stage in accordance with requested energy and a laser power source control device that at least changes pump intensity of discharge electrodes in said amplifier stage in accordance with said requested energy, in a case where the energy of laser output light from said laser device is to be changed discontinuously in response to a request from an exposure apparatus.