The customized training in vocational colleges has been regarded as a effective pathway for school-to-work transition of students in vocational colleges. However, actual performances of the customized training were not proven sufficiently. Being based upon this situation, this paper aimed at analyzing what performances the customized training have brought about in industrial firms which employed graduates who had joined the customized training programs in vocational colleges. A questionnaire survey was carried out to analyze performances. It included two hundreds of industrial firms in sixteen provincial areas. Variables included in the survey were those ones which could prove the performances of education by the customized training programs, such as job competencies, employment ratio, productivity. The main method adopted for data analysis was the comparison of performances of education between those employees who joined the customized training programs in vocational colleges and their counterparts who didn't joined the programs. According to the major findings of the study, industrial firms showed higher positive responses on job competencies, employment ratio, productivity, decrease of education cost of the employees who joined the customized training programs in vocational colleges than their counterparts. Also, large-sized industrial firms and large city-located industrial firms recognized higher performances of the customized training than small to midium -sized ones and small city-located ones. This finding showed the relevant relationship between performances of the customized training and the size and regional location of the industrial firms. High recognition of industrial firms on performances of the customized training suggests that the expansion of the customized training programs based on strong school-industry cooperation is needed. Besides, results of the study suggest that the Government is needed to take greater initiatives in supporting the customized training programs. These initiatives need to be focused on to support vocational colleges in acquiring the facility and equipment needed for practical training, to provide information on industrial trends, shift in work responsibilities and employment opportunities, and to assist in selecting the appropriate OJT provider, and monitoring of training activities in the field.