PURPOSE: To provide an apparatus which allows liquid level detection without trouble even when the intended liquid is mixed with non-conductive substance or poor in conductivity by vertically arranging a movement passage of conductive liquid in a lift guide so constructed that the floating attitude changes depending on the variation in the liquid level.

CONSTITUTION: A lift guide 1 having a mobile float 2 inserted thereinto changes in the floating attitude sensitive to variations in the liquid level tied with a cable or the like. It is provided with a passage port 4 cut on the surrounding wall thereof, a movement passage 5 through which a conductive liquid flows freely and an electrode switch 7. The conductive fluid 6 such as water is allowed to flow downward according to the variation in the attitude of the lift guide and a control tappet 8 of the liquid is provided to check eary action of the switch 7. The guide 1 descending turns the tip downward when the liquid level in a tank reaches the lower limit l1 while the guide ascending turns the tip upward when the level reaches the upper limit l2. At this point, the liquid 6 touches the electrode of the switch 7 thereby indicating the level.