We introduced the application of a planetary centrifugal mixer to dispensing powdered medicines to prevent from individual variation in the skills of pharmacists with a manual blending. The blending performance of the mixer was explored in terms of four operational variables, namely, operation speed (400-1000 rpm), operation time (10-60 s), charging rate in vessel (20-50%), and size of vessel (35, 58, 125, 550 mL), using colored lactose and crystalline lactose as the principle model medicine and diluent, respectively. The blending degree was assessed by image analysis, so the extent of uniformity was expressed as the relative standard deviation of the color difference signal Cb value of YCrCb color space. Application of the mixer to blending three commercial medicines with diluents was carried out. Sufficient blending was achieved at 10 s using a 20% charging rate and 35 mL vessel irrespective of operation speed. As the charging rate was increased, a higher operation speed was needed to obtain uniform blending. A larger sized vessel also required a higher operation speed. Uniform blending was achieved in all of the mixtures of colored lactose and crystalline lactose at the weight ratio of 1 : 9-9 : 1. In the application studies using Adona®, Anginal® and Neophylline® powder, the blending performance of the mixer was equivalent to that of the manual blending method, showing relative standard deviations of 2.2-3.3% and 1.8-3.8%, respectively. These results revealed that the planetary centrifugal mixer was suitable for blending powdered medicine.