網路消費者對於線上付款及個人帳戶資料安全等疑慮，致使我國電子商務發展受到限制，反觀第三方支付服務於國外已行之有年，且成效良好。2012年初我國始放行此項金流服務，然發展至今，使用尚未廣泛普及，以網路交易者觀點探討第三方支付服務仍為罕見。本研究旨在探討影響網路交易者使用第三方支付服務意圖之關鍵因素，期研究結果可供主管機關及業者開發導入之參考。 本研究採問卷調查法蒐集資料，以某非金融機構建置第三方支付服務為標的，探討創新擴散、制度型信任、知覺風險與採用意願之關聯性。研究結果顯示，創新擴散之相對優勢、複雜性及可觀察性顯著影響網路交易者採用第三方支付服務之意願。網路交易者對第三方支付服務之制度型信任機制越信任，越可降低對該服務之知覺風險；知覺第三方支付服務風險之降低，採用意願則越高。研究亦發現，網路交易者對第三方支付服務制度型信任機制之信任感，可透過知覺風險之降低，間接增加使用者之採用意願。 As online consumers are concerned about the security of online payment and personal account data that influences the development of e-commerce. However, the third-party payment service that has developed for many years maintains its growth in a sound way in variety countries. The online payment service in this regard began in Taiwan in 2012, then development so far, that has not been widely available and there are still few studies on third-party payment service from the perspective of internet traders. This study aims to discuss the key factors that affect internet trader’s intention of using third-party payment service, and the research results are expected to provide references for competent authorities and dealers’ development. With a non-financial institution that set up the third-party payment service as the research subject, the study adopted the questionnaire survey to collect data and then discussed the relationship between diffusion of innovations, institution based trust, perceived risk and adoption intention. The results indicate that the comparative advantage, complexity and observability of diffusion of innovations have significant impact on internet trader’s intention of using the third-party payment service. The more internet traders trust the institution based trust mechanism of the third-party payment service, the less perceived risk of the service they have; the better the effect of reducing perceived risk of the third-party payment service, the more adoption intention they have. It is also found out that internet traders’ sense of trust to institution based trust mechanism of the third-party payment service can indirectly increase users’ adoption intention by perceived risk reduction.