PURPOSE: To provide a flowsensor preventing well the runner shaft vibration.

CONSTITUTION: Provided are a cylindrical case 4 formed of a flow inlet 3 at the bottom, a runner 6 having a magnet and contained in the case 4 which is directing its rotation shaft vertical direction and changes the number of revolution according to the flow from the inlet 3, and a detection means which detects the change in the magnetic field due to the change in the number of revolution of the runner 6 and detects the flowrate. At the top and the bottom of the case 4, shaft containers 14, 11 which contain a rotation shaft 7 of the runner 6 rotationablly and movablly to the shaft direction and have larger inner diameters than the rotation shaft 7 diameter, are formed. At the top end surface of the rotation shaft 7, a projection 17 for reducing the contact area to the end of the shaft container 14 at the top end side, and at the end of the shaft container 14, a spherical concave part 14a is formed.