PURPOSE: To detect the rotation with high resolution without using a magnetic sensitivity element, by providing a rotatable conducting shaft and a conductive fixed shaft, to which wings that are overlapped with blades and made to form capacitors with a gap being provided from the blades are attached.

CONSTITUTION: The central part of a magnet 5 is fixed to the lower end part of a conducting shaft 8 through an insulating member 7. Said conducting shaft 8 is rotatably supported by the upper and lower plates of an insulating case 9. A conductive fixed shaft 14 is electrically connected to an external electric circuit. A plurality of conducting wings 15, which can be overlapped with rotary blades 13, are horizontally attached and fixed to the fixed shaft 14, with a gap being provided from the rotary blades 13. Capacitors are formed by the wings 15 and the rotary blades 13. The rotation of the measuring part of a flowmeter is converted into the variation of the electric capacities caused by the overlap of the rotary blades and the conducting wings and the result is detected. Therefore the rotation can be detected with high resolution without using a magnetic sensitivity element.