This study was undertaken to develop the scapulometer, a measuring tool for scapular winging, and to determine the reliability of scapulometer. Thirty subjects with scapular winging greater than 2 cm participated in this study. Two examiners measured scapular winging using the scapulometer. Standardized measurement position of each subject was as follows: neutral position of shoulder and wrist, $90^{circ}$ flexion of elbow, and cuff weight of 5% and 10% of body weight (BW) to neutral wrist. The interrater and intrarater reliability were calculated with an intraclass correlation coefficient (ICC) with 95% confidence interval (CI) and standard error of measurement (SEM) at 5% BW and 10% BW. The level of scapular winging was tested between 5% BW and 10% BW with a paired t-test. The interrater reliability was shown to be high at 5% BW (ICC(2,k)=.955, 95% CI=.900~.979, SEM=.07) and at 10% BW (ICC(2,k)=.968, 95% CI=.930~.985, SEM=.06). The intrarater reliability was shown to be high at 5% BW (ICC(2,k)=.921, 95% CI=.842~.961, SEM=.09) and at 10% BW (ICC(2,k)=.906, 95% CI=.813~.954, SEM=.10). The level of scapular winging was significantly different between 5% BW and 10% BW. Conclusively, it is demonstrated that the scapulometer is an objective and qualitative measurement tool for scapular winging.