Alignment system and extreme ultraviolet light generation system

An alignment system for use with a laser apparatus, comprising:

• a guide laser device configured to output a guide laser beam;
• an adjusting mechanism configured to adjust a travel direction of at least one of the guide laser beam and a laser beam from the laser apparatus;
• a beam path combiner configured to control a travel direction of the laser beam and a travel direction of the guide laser beam to substantially coincide with each other;
• a first optical detection unit provided downstream from the beam path combiner and configured to detect the laser beam and the guide laser beam;
• a first controller configured to control the adjusting mechanism based on a detection result of the first optical detection unit;
• a beam steering unit provided downstream from the beam path combiner and configured to control travel directions of the laser beam and the guide laser beam;
• a second optical detection unit provided downstream from the beam steering unit and configured to detect at least the guide laser beam;
• and
• a second controller configured to control the beam steering unit based on a detection result of the second optical detection unit.