An exposure system that performs scanning exposure of a semiconductor substrate by irradiating a reticle with a pulse laser beam includes a laser apparatus configured to emit a pulse laser beam, an illumination optical system through which the pulse laser beam is guided to the reticle, a reticle stage, and a processor configured to control emission of the pulse laser beam from the laser apparatus and movement of the reticle by the reticle stage. The reticle includes a region in which multiple kinds of patterns are arranged in a mixed manner in a scanning width direction orthogonal to a scanning direction of the scanning exposure. The processor instructs the laser apparatus about a target wavelength such that the laser apparatus emits the pulse laser beam of a wavelength with which dispersion of best focus positions corresponding to respective patterns of the multiple kinds of patterns is minimum.