Purpose: While an unmanned helicopter has been extensively used for spraying chemicals on agricultural crops, its low utilization (two months per year from July to August) has recently become an issue. This study aimed to increase the utilization of the unmanned helicopter. The centrifugal rice seeder, a mounting device for rice seeding for unmanned helicopter was developed and assessed its performance. Methods: The concept of the centrifugal spraying device was to obtain design criteria for centrifugal distribution. Four types of blade shapes namely straight, curved, straight wing and curved wing were developed and used. The rotational speed of the blades was tested at 1,000, 1,200 and 1,400 rpm. Results: The blade shapes, rotational blade speed and angle of trajectory were theoretically analyzed and results were validated with a series of laboratory experiments. Conclusions: The curved wing blades provided the distribution uniformity (DU) at 1,200rpm of rotational speed and 60 degree of seed drop point. The spray uniformity of 4.2% was also achieved.