A liquid viscosity detecting method is performed in a liquid droplet ejecting device that includes a piezoelectric type droplet ejecting head to which a drive waveform is applied to pressurize a liquid chamber to eject a liquid droplet, a drive waveform generator to apply the drive waveform to the droplet ejecting head, and a residual vibration detector. The method includes detecting, by the residual vibration detector, amplitude values of multiple cycles of a residual vibration waveform occurring within the liquid chamber after the drive waveform is applied; calculating an attenuation ratio based on the amplitude values; and calculating a liquid viscosity in the liquid chamber based on the attenuation ratio.
