The present invention relates to a spray device of a pest control vehicle which sprays medicinal liquids through high-pressure air flow to prevent damage to plants in forests, fields, or orchards from harmful insects, and a method of improving a pest control effect and reducing amounts of medicinal liquids unnecessarily wasted during pest control by controlling a blast pressure according to a distance from an object in need of pest control and a spray angle. According to an embodiment of the present invention, the spray device includes: a rotation means for rotating a rotator providing blast air a controller for controlling the rotation means and a measurement sensor for measuring a distance from an object in need of pest control, and transferring the same to the controller. A blast pressure is controlled by automatically controlling a rotation rate of the rotator according to a measured value of the measurement sensor, that is, the distance from the object, so that medicinal liquids can be suitably sprayed according to heights and distances of fruit trees. According to another embodiment of the present invention, the spray device includes: a body spray nozzle for spraying in a side direction that has almost no effect from gravity and a first blast hole and a second blast hole operated by the rotation of the rotator to change a spray capacity of a duct spray nozzle spraying the medical liquids in an upper-side direction which is under the effect of gravity. The first blast hole communicates with the body nozzle and the second blast hole communicates with the duct nozzle, and the first blast hole has a greater cross-sectional area than that of the second blast hole. It is possible to provide a plurality of second blast holes which offer stronger spray capacity by the fast flow of blast air due to smaller channel cross-sectional areas than those of first blast holes, and communicate with the duct spray nozzle to not affect spray amounts.COPYRIGHT KIPO 2016본 발명은 임야나 과수
