This paper attempts to present the development of English vocabulary application for high school and university students based on The Common European Framework of Reference for Languages (CEFR)  with the prototype. Research procedures consist of three main phases. In phase 1, in order to find out English vocabulary problems and needs, undergraduate students at Nakhon Pathom Rajabhat University (NPRU) were assigned to complete a needs analysis questionnaire. In phase 2, based on the needs analysis results, the prototyping model was designed. It was then presented to the users (NPRU students) in order to receive feedback.  In the last phase, the application was developed, pilot-tested by the application developers, and implemented by the users (NPRU students). The application was then improved and finally published. Findings shed light on the needs of working functions, application screen icons for vocabulary learning, and methods to develop application adopting the prototyping model.