Education in Indonesia is currently experiencing a curriculum change from the 2013 Curriculum to the Merdeka Belajar curriculum where natural science and social science learning subjects need to be combined into one unit, which we then call the term IPAS. In IPAS learning, there are 2 main elements: understanding IPAS (science and social) and Process skills. But in reality, the assessment of process skills in schools is rarely done. This study aims to develop an assessment instrument to measure fifth-grade students' science process skills (SPS) in all Madrasah Ibtidaiyah Negeri (MIN) in Pontianak City. The questions were developed using the 4D technique. The questions developed were then validated by 2 experts using the Gregory technique. Furthermore, the questions were distributed to all MIN in Pontianak City to determine their reliability. The results showed that based on expert assessment, the KPS questions developed had a very high validity category both in terms of material, construction, and language. Furthermore, based on the results of the trial at MIN in Pontianak City, the reliability value of the question was 0.41 with moderate criteria, therefore, it can be said that the developed questions are valid and reliable to be used as an instrument to measure the science process skills of fifth-grade students.