A laser system includes: a laser light source; a light detector configured to output an electric current proportional to an output laser light of the laser light source; a resistor network configured to convert the electric current output from the light detector to a monitor voltage; and a regulator configured to control an intensity of the output laser light based on a comparison between the monitor voltage and a voltage corresponding to a control target value, wherein the resistor network comprises at least two branch circuits connected in parallel with each other, and the branch circuits include respective digital potentiometer circuits commonly formed in a single device.