is also angularly moved so that the magnet 53 passes by the microswitch 52 mounted on the nozzle barrel 21 near the change over valve 40 so that the switch 52 is turned on whereby a pulse signal given from the controlling device 15 through the cable 51 so as to actuate the sensor 31 and an echo signal caused thereby is given to the controlling device the cable 51 is preferably extended in the air duct 13b now in operation of the fuel dispenser as referred to above referring to fig5 when taking off the nozzle 20 from the hook 19 the nozzle switch 18 is turned on step a so that the indicator 16 is reset to 34 zero 34 and the air pump 13 is driven step b since the nozzle lever 23 is not yet triggered on this step the main valve is retained in the closed position and the change over valve body 43 is in the first or close position so that air fed from the air pump 13 through the air hose 13b passes the air tube 34 for sweeping air in the chamber 30 possibly containing fuel vapor therefrom and exhauseted out of the tip opening 26 into the atmosphere when inserting the tip of the nozzle 20 into the vehicle fuel tank and triggering the nozzle lever 23 the magnet 53 mounted at the free end of the angularly moving arm 45 passes by the microswitch 52 to be turned on step c and the change over valve body 43 is moved to be in the second or open position for ejecting air into the atmosphere.