Line narrowed laser apparatus

A line narrowed laser apparatus configured to perform a plurality of burst oscillations including a first burst oscillation and a second burst oscillation next to the first burst oscillation to output a pulse laser beam, comprising:

• a laser resonator;
• a first chamber provided in the laser resonator;
• a first pair of electrodes provided in the first chamber;
• a first electric power source configured to apply pulsed voltage to the first pair of electrodes;
• a wavelength selecting element provided in the laser resonator;
• a second chamber provided in an optical path of the pulse laser beam outputted from the laser resonator;
• a second pair of electrodes provided in the second chamber;
• a second electric power source configured to apply pulsed voltage to the second pair of electrodes;
• and
• a controller configured to measure a duty in a predetermined period before starting the second burst oscillation and a length of a suspension period from a time of ending the first burst oscillation to a time of starting the second burst oscillation, and performs a first control of a difference between a timing of a first electric discharge between the first pair of electrodes and a timing of a second electric discharge between the second pair of electrodes based on the duty and the length of the suspension period.