A beam delivery system may include: beam adjusters configured to adjust a divergence angle of a pulse laser beam; a beam sampler configured to separate a part of the pulse laser beam outputted from a first beam adjuster provided at the most downstream among the beam adjusters to acquire a sample beam; a beam monitor configured to receive the sample beam and output a monitored diameter; and a beam delivery controller configured to control the beam adjusters based on the monitored diameter. The beam delivery controller may adjust each of beam adjusters other than the first beam adjuster selected one after another from the most upstream so that the monitored diameter at the beam monitor becomes a predetermined value specific to the beam adjuster, and adjust the first beam adjuster so that the pulse laser beam becomes focused at a position downstream of a target position.