Research has been conducted to develop a physics learning media in the form of an Android-based pocket book. We designed a Harmonic Oscillation Pocket Book and tested its feasibility and effectiveness in improving the cognitive learning outcomes of students. This study used the research and development method adapted from the ADDIE model. The results revealed that this software has been successfully developed and is very feasible to be used as a physics learning medium. This Android-based Harmonic Oscillation Pocket Book was effective in enhancing the students' cognitive learning outcomes, and students showed a tendency to respond positively to the software.