Assessment is one of the components of the teaching process. In education, the quality of assessing student learning outcomes is a criterion for the quality of education. With that role, assessment is expected to bring a lot of value to learners, but in reality, there are still many difficulties. The purpose of the study is to understand the factors affecting the quality of assessment of learning outcomes from the perspective of students in primary education. The exploratory factor analysis (EFA) method was used to extract the factors and was performed through SPSS software. The results from 893 students of 6 universities show that there are 8 main factors affecting the quality of assessment of learning outcomes including assessment principles, feedback methods, information-handling instructions, satisfaction levels, facilitating conditions, relationship with teaching elements, self-assessment and assessment process. The findings of this study enrich the theoretical framework and serve as a reference for educators and policymakers.