A measurement unit obtains, when a droplet ejected from an ejecting head
adheres to an electrode of a crystal oscillator, a viscosity and a mass
of the droplet on the basis of a changed value in resonance frequency and
of a resonance resistance of crystal oscillator. Measurement unit then
supplies to a control unit droplet information ID showing the obtained
viscosity and mass. Control unit determines, on the basis of the
viscosity and the mass included in droplet information ID, an appropriate
drive waveform to be supplied to ejecting head.