Software Engineering must face the new challenges imposed by the Cloud Computing paradigm. New methodologies for software development must be proposed. For this purpose, this paper presents a specific methodology for collaborative software development in the Cloud, and then describes the architecture of Automatic Software Development as a Service (ASDaaS). The goal of ASDaaS is to popularize software development in the Cloud and make it accessible to non-IT professionals. In fact, with Cloud Computing and the convergence toward “Everything as a Service”, we no longer consider the classical context of software development, where IT teams or integrators are solicited to perform software development. ASDaaS allows a stakeholder, without computer skills to perform automatic developments from functional requirements, SLA (Service Level Agreement) requirements, and business rules definition. ASDaaS promotes the discovery and composition of web services. It is itself composed of a set of services which can carry out and cover the whole process of software development. ASDaaS also allows the automatic development on Cloud platforms of undiscovered services by model transformation. Indeed, for each new development, a choice of PaaS (Platform as a Service) is performed by matching development constraints imposed by the stakeholder, with the features and services offered by the Cloud Platform.