This research studied the relations-hips among external variables, internal variables, and employee intention of knowledge sharing in the Theory of Planned Behavior. Industrial Technology Research Institute in Taiwan is chosen as the case under study. A questionnaire survey has been done respectively in two research groups which represent senior R&D employee and members in community of practice of knowledge management, in order to find out the major determinants of employee intention of knowledge sharing. In conclusion, it has positive influences on employee intention of knowledge sharing by reinforcing the cooperative work relationship within employees and activating altruistic motive of knowledge sharing. In addition, it is helpful for knowledge sharing contexture by building up a trustful organizational culture and adopting proper managerial system.