PURPOSE: To enable exact detection of a liquid amt. by providing a holder which is so constructed as to increase the creeping length between a pair of electrodes forming a detecting capacity in the lower part of said electrodes.

CONSTITUTION: The flow rate of liquid is detected in accordance with the change in the electrostatic capacity value of the detecting capacity formed by a pair of electrodes 11, 12. Since the electrodes 11, 12 have a long detecting length, a holder 8 is provided to the top end of the electrodes in order to prevent the change in the space between the electrodes owing to an oscillation or the like and the consequent change in the detecting position of the flow rate. A projection 81 is provided to the intermediate part of the holder 8 to increase the creeping length between the electrodes. Sticking of the liquid to the holder 8 by surface tension and the consequent erroneous detection are thus prevented by the projection 81. The liquid amt. is thus exactly detected.