To provide a system for spraying pesticide that can improve the working and energy efficiencies, in addition, can increase the degree of freedom on the starting and returning places for the spraying helicopter.

The ignition timing is detected by means of the ignition pulser coil 11, and the engine rotation calculator 632 calculates the rotation number of the engine for the unmanned helicopter as it receives the signals relating to the engine rotation output from the waveform shaping circuit. Then, the spray width calculator 633 judges whether the engine rotation is judged to be more than the moderate rotation or not. In the case that the rotation is more than the moderate one (judged that the unmanned helicopter has taken off from the ground and risen in the air), the motor 263 is allowed to rotate at high rotation to complete the preparation for the pesticide application by allow the motor 263 to rotate at a high speed.