In a liquid discharging device, an objective optical system is moved in the optical axis direction by a focus position adjusting mechanism to perform a first focusing action relative to the tip of a liquid discharging nozzle or a mirror image thereof and a second focusing action relative to the surface of a substrate facing the liquid discharging nozzle, the distance between the nozzle tip and the surface of the substrate is calculated on the basis of the resulting focus positions, and the position of the liquid discharging nozzle is adjusted by nozzle position adjusting mechanism so that the gap is appropriate. According to this configuration, the distance between the nozzle tip and the surface of the substrate can be precisely calculated and an optical unit for observation can be focused on the surface of the substrate.