Software Engineering must face the new challenges imposed by theCloud Computing paradigm. New methodologies for software development mustbe proposed. For this purpose, this paper presents a specific methodology for collaborativesoftware development in the Cloud, and then describes the architectureof Automatic Software Development as a Service (ASDaaS). The goal ofASDaaS is to popularize software development in the Cloud and make it accessibleto non-IT professionals. In fact, with Cloud Computing and the convergencetoward “Everything as a Service”, we no longer consider the classical contextof software development, where IT teams or integrators are solicited to performsoftware development. ASDaaS allows a stakeholder, without computerskills to perform automatic developments from functional requirements, SLA(Service Level Agreement) requirements, and business rules definition. ASDaaSpromotes the discovery and composition of web services. It is itself composed ofa set of services which can carry out and cover the whole process of software development.ASDaaS also allows the automatic development on Cloud platformsof undiscovered services by model transformation. Indeed, for each new development,a choice of PaaS (Platform as a Service) is performed by matching developmentconstraints imposed by the stakeholder, with the features and servicesoffered by the Cloud Platform.