Recently, public libraries have increased in quantity, while various problems have arisen regarding the operation of public libraries, such as lack of librarian manpower and facilities. Additionally, an increase in the number of public libraries does not correlate to an increase in the utilization of public libraries, and thus developing various services is needed to maintain the continued use of public libraries. This study examined which types of use motivations affect the intention of knowledge exchange in public libraries when using public libraries based on the self-determination theory. It also looked at how the use motivations and the intention of knowledge exchange vary depending on the frequency of public library use. According to an online survey of 230 users of public libraries, extrinsic motivation, intrinsic motivation, autonomy, competence, and relatedness as independent variables had a positive impact on the level of knowledge exchange. In addition, the higher the frequency of public library use, the higher the needs for autonomy and relatedness were. Based on the results, it was suggested that the knowledge exchange needs to be established as a new service of public libraries by offsetting extrinsic motivation that emerged from by negative influences and promoting intrinsic motivation, autonomy and competence.