A liquid level detector includes: a detecting element having one surface and the other surface opposite to the one surface, the one surface being opposed to a liquid, while being parallel to a height direction of liquid level; a Peltier element provided on the other surface side of the detecting element; and a control unit performing a detection processing for a liquid level of the liquid. The Peltier element forms a heat flow passing through the detecting element from the other surface to the one surface, toward the liquid or a gas. The control unit calculates a liquid level on the basis of an output value of an electrical signal outputted according to the heat flow passing through the detecting element, and a relationship between an output value of the detecting element and a liquid level.