The purpose of this study is to verify the competence level of IT service companies in Korea from the view point of capability of creating customers value and outcome as an independent companies which have been growing in the captive customers(market) circumstance by performance data analysis and IT specialists survey. This study presents a growth model which emphasis on the importance of the correlation between IT service companies and captive customers. It proves that the captive customers have been being the growth power and motive of the IT service company, because IT service companies have been cumulating the competence for IT service through the service for the customers, and with this competence, IT service companies have been expanding its service out to non-captive market(customers) and got good outcomes as an independent companies. And this study proves that the captive customers who served by the IT service companies which have a higher level of service capabilities have better business outcome. IT service companies contribute to improve the IT level of the captive customers and to make the customers to increase sales by conducting IT projects.