1. A target generation device, comprising: a target generator configured to be driven by a pulse voltage to generate a droplet of a target material; a detector configured to detect a target generated by the target generator and output a detection signal indicative of a detection result; and a controller configured to, responsive to the detection signal: determine whether or not a target is generated by the target generator based on the detection signal, and determine whether or not the generated target includes a plurality of droplets, and control a pulse duration of the pulse voltage for driving the target generator when the generated target includes the plurality of droplets.