The development of cloud computing has promoted Software as a Service (SaaS) as another option for firms to adopt IT services. Many studies have confirmed the advantages of SaaS, while seldom conducted case studies on the implementation of SaaS. This research investigated the Top 2000 firms of Taiwan and constructed a research structure based on task/technology fit (TTF), joint benefit, and relationship viewpoints for analysis with PLS. The results show that although firms consider SaaS as a good solution for IT, they have no intention of adoption. The findings can help SaaS vendors to develop business strategies when designing future service models.