PURPOSE: To achieve a cost reduction and a smaller size of an inkjet recorder or the like by a method wherein an alarm is outputted when the liquid level in a tank is below the specified value while a different alarm is outputted when the liquid level therein is below the specified value even after the action of supplying a liquid to the tank according to the former alarm.

CONSTITUTION: The resistance Rx between electrode pairs 9 becomes infinite when the position of the ink liquid surface in a sub ink tank 4 is lower than the electrode pairs 9. An intermittent signal P2 is introduced to the base of a transistor T2, which is turned ON or OFF intermittently while a LED23 is flashed intermittently. When a working switch 15a of a pump 15 is turned ON to perform a forced supply of ink to the sub ink tank 4 with a suction cap 16 according to the alarm, a continuous high level output of an NAND gate 26 is introduced to the base of the transistor T2 to light the LED23 continuously. But when the main ink tank 12 runs out of ink, the lighting of the LED23 continues.