The Gross Motor Function Measure (GMFM) is an internationally widely used outcome measure. The aim of this study was to evaluate the structural properties of the Korean version of GMFM using the Rasch Model, with regard to scoring within rehabilitation centers in Korea. GMFM data for 206 children with cerebral palsy were collected from 11 outpatient rehabilitation facilities by 29 pediatric therapists. The Winsteps software was used to refine the rating scale. This study suggests that the scoring categories of the Korean version of the GMFM should be collapsed from 0 (subject does not initiate task), 1 (subject initiates task), 2 (subject partially completes task), 3 (subject completes task) to 0 (subject does not initiate task), 1 (subject initiates or partially completes task), 2 (subject completes task) for better accuracy in estimating the gross motor function of children with cerebral palsy.