網際網路技術促進了社群網路服務 (Social Network Sites, SNS) 發展，數年來藉由成員間互動分享與經驗累積成為現今大眾常用的知識分享工具，其中以虛擬社群最常為一般大眾所使用，其知識的流動效率決定了虛擬社群能否存活的關鍵。但就社群管理面而言，如何有效推動社群成員提供知識以及吸引使用者接收知識動機，至今仍未有定論。過去學者大都以單一個人層次或組織層次分析知識分享行為，本研究整合社會認知理論與社會交換理論觀點，提供另一跨層次觀點檢驗個人層次與社群環境層次的整合效果，建構出知識分享在知識提供行為及知識接收行為的研究模式。意義在探討使用者在虛擬社群的知識分享行為是如何受到外在環境、個人自我認知概念因素的影響。研究從28個虛擬社群進行三年追蹤，共回收552份問卷進行階層線性模型 (Hierarchical Linear Modeling, HLM)實證。研究結果發現個人對知識易用性能影響知識自我效能並促進知識分享的提供行為。另一方面，在外在社群環境氛圍下社群規範能促進知識提供行為，而社群信任能有效提昇知識接收行為。社群互惠對知識提供與知識接收行為皆有所助益。;Over the years, internet technology has promoted the development of social network sites (SNS), and has also become the most frequently-used knowledge-sharing tool through the interactions between members. However, from the perspective of the community management, it is still undecided as to how to effectively promote the knowledge provided between community members and attract users to receive knowledge. Most research papers in the past mainly focused on analyzing knowledge-sharing behavior based on either the individual or organizational levels. Combining aspects of social cognitive theory and social exchange theory, this study provides another cross-level perspective to examine the integration effect on the basis of the individual and community environment levels, and establishes a research model of knowledge-providing and -receiving behaviors. The purpose of this study is to explore how users′ knowledge-sharing behavior in virtual communities is affected by the external environment and by the personal cognitive factor. This study investigates 28 virtual communities over three years, yielding 552 valid questionnaire testing results through hierarchical linear modeling (HLM). The findings of this study reveal that perceived ease of use affects knowledge self-efficacy and also promotes knowledge-providing behavior on an individual aspect. On the other hand, community norms can encourage knowledge-providing behavior in the external community environment. Moreover, community trust can effectively enhance knowledge-receiving behavior, and community reciprocal can also promote knowledge-providing and -receiving behavior.