The purpose of this study was to analyze student errors in solving algebraic operations problems based on Watson's criteria. This type of research is descriptive qualitative research with a qualitative approach. The research subjects were 2 low error students, 2 medium error students, and 2 high error students. The instrument used is a written test about the operation of algebraic forms and interviews. Checking the validity of the findings using a source triangulation technique, namely, by comparing student test results and interview results. Based on the results of the study, the types of errors made by students were incorrect data, incorrect procedures, missing data, missing conclusions, skill hierarchy problems, response level conflicts, and indirect manipulation. The results of this study are expected to be input for teachers about the types of errors of students at SMP PGRI 6 Malang.