To provide a liquid level detector capable of detecting stably, even if a liquid storage container (or a tank) vibrates and measuring a position of liquid level with a high, resolution and moreover, even near basal plane of a liquid storage container.

The liquid level detector is arranged inside a tank 38, where the vertical direction is adopted as an axis and includes a cylindrical member 51, having a liquid mouth 51d at the lower part thereof and an air hatch 51c at the upper part thereof and an ultrasonic sensor 52 (or a distance sensor), arranged at the upper end of the cylindrical member 51 for detecting the distance until a liquid level FL of the cylindrical member 51 in a noncontact manner, and sends an output from the ultrasonic sensor 52, as a signal indicating the position of the liquid level FL in the tank 38.