This textbook deals with design research which is close to action research. Differences between the concepts of action research and design research are very fine. Design research is based on development work that includes research. The opening chapters cover research approaches and how design research fits into the field of research. The book provides a step-by-step guide for a student in planning, realising and reporting of a thesis intended as design research. The book is practice oriented, and the author guarantees success in completing a thesis with its help. The book pays particular attention to credibility and how to write a report based on research materials and results. The latter part of the book includes a separate component on general evaluation criteria for theses, and provided that a writer familiarises themselves with them, it is possible to ensure that the work intended as a thesis also satisfies the scientific criteria and will be approved at an academic educational institution. The author of the textbook has taught methodology for many years and has written several textbooks on qualitative, quantitative and action research.