To provide a chemical spraying device for an unmanned helicopter capable of performing air-bleeding work of a chemical conveying passage without releasing the chemical to the outside of the airframe.

The chemical spraying device 5 provided with chemical tanks 51L, 51R for storing the chemical; pumps 52L, 52R for pressure-feeding the chemical; nozzles 55L, 55L, 55L, 55R, 55R, 5R for spraying the chemical; the chemical conveying route for conveying the chemical to the nozzles via pumps from the chemical tanks; a chemical returning route communicating a midway part of the chemical conveying route, i.e., a downstream side than the pumps and an upstream side than the nozzles with the chemical tanks; and an opening/closing valve 60 provided on the midway part or an end of the chemical returning route is provided on the unmanned helicopter 1 operated by a radio operation means 80.