AbstrakPembelajaran di abad 21 sangat memerlukan berbagai inovasi media pembelajaran yang dapat dijadikan sebagai alat bantu pendidik dalam melaksanakan kurikulum. Buku saku digital berbasis science, technology, engineering, and mathematics (STEM) bertujuan agar dapat dikembangkan menjadi media pembelajaran yang layak dan menarik terhadap kemampuan pemecahan masalah. Metode penelitian yang digunakan adalah Reseach and Depelovment (R&D) dengan menggunakan model ADDIE. Teknik analisis data menggunakan teknik deskriptif kualitatif serta kuantitatif. Proses uji coba dilakukan setelah validasi ahli materi dan ahli media yang menunjukkan bahwa buku saku berbasis STEM memiliki kriteria menarik untuk digunakan. Namun uji efektivitas media pembelajaran buku saku digital tidak dapat terlaksana disebabkan adanya pandemi covid-19 yang mengakibatkan kegiatan pembelajaran dilakukan secara daring atau online. Adanya kebijakan tersebut mengakibatkan penelitian ini hanya terlaksana sampai pada tahap development atau pengembangan. STEM-Based Digital Pocketbook: Development of Learning Media on Students' Mathematical Problem-Solving Skills AbstractThe 21st century needs a variety of learning media innovations that can be used as a device in implementing the curriculum. The goal of digital pocketbooks based on science, technology, engineering, and mathematics (STEM) is to develop into worthy and interesting learning media on mathematical problem-solving skills. The research method used Research and Development (R&D) using the ADDIE model. Data analysis techniques use qualitative and quantitative descriptive techniques. The process was conducted after validation of material experts and media experts who showed that STEM-based pocketbooks had interesting criteria to use. However, the effectiveness of digital pocketbook learning media cannot be carried out due to the covid-19 pandemic that resulted in learning activities being conducted online or online. The existence of this policy resulted in this research only being carried out to the stage of development or development.