A target supply device may include a reservoir configured to hold a target material in its interior in liquid form, a vibrating element configured to apply vibrations to the reservoir, a target sensor configured to detect droplets of the target material outputted from the reservoir, a control unit configured to set parameters based on a result of the detection performed by the target sensor, a function generator configured to generate an electrical signal having a waveform based on the parameters, and a power source configured to apply a driving voltage to the vibrating element in accordance with the electrical signal.