The purpose of this paper is to propose an analytical framework to explain why knowledge intensive business services (KIBS) have become an important strategy for many firms. It will especially examine why the relationships between KIBS and clients are different by analyzing the impact of KIBS for different types of innovation and different divisions, and also what and how the service delivery method contributes to each type of innovation for Japanese manufacturing corporations (JMCs). The results show that firstly, KIBS provide professional knowledge to accelerate the different innovation of their clients; secondly, KIBS contribute more to the radical innovation of a client than incremental innovation; and the thirdly, face-to-face delivery is the most efficient method of service from KIBS to the JMCs.