A SaaS cloud service represents a model deployed and running on a cloud platform to enable users to use software as an online service. This work proposes a development methodology adequate for the effective development of SaaS cloud services. For doing this, we first analyzed the current state of companies developing SaaS cloud services and identified key factors for the development of SaaS cloud services. Then, we selected and tailored the methodology that is best suited for the development of SaaS cloud services among existing software development methodologies. To validate the applicability of the proposed methodology, we performed a case study tailoring the development methodology adequate for the company developing SaaS cloud services.