This paper explains and demonstrates how open innovation can be done in a small firm from idea generation phase through product development to marketing. It has been possible to see open innovation case studies of big companies such as IBM, Intel, or 3M(Chesbrough, 2003)and there are also a lot of survey based studies done about small and big firms(Van de et al., 2008, (Laursen & Salter, 2006). But, it appears there have not been studies that look into the open innovation realities of small firms in full detail. It can be argues that open innovation for small firms,which do not have enough R&D resources and/or internal researchers, is essential for their survival and development. In this study, we will look into the open innovation of a small firm in the total process of product development and marketing. In the process of new product development, a small firm should do active open innovation to overcome the limitation of internal technology and research capability. In the end, at the marketing phase, small firms should utilize outsourcing or outside capacities. In this research, we will find out about real open innovation from idea generation through new product development to marketing in a small firm by way of a case study of a Korean SME.