It is important to determine the behaviors of primary school pre-service teachers, who have successfully completed the "Mathematics Textbook Review" course during their undergraduate education, regarding the use of textbooks in their professional life. Therefore, it is important to determine the approaches of pre-service teachers who have positive ideas about using the mathematics textbook in their undergraduate education and the reasons for these approaches in the process after starting the profession. This research was designed with a developmental perspective from qualitative research approaches and was conducted with two different study groups in Turkey. The first study group consists of 162 primary school mathematics pre-service teachers. The second group consists of 43 primary school mathematics teachers who worked for at least two years in their professional life. As a result of the research, more than half of the pre-service teachers (n=132) stated that they would use textbooks as a basic resource in the in-class teaching process. Pre-service teachers' reasons for using the course book in the classroom teaching process were grouped under four categories: "it is a guide for teaching, homework, affordability, and opportunity for repetition". When the data obtained from the mathematics teachers were examined, it was determined that most of the teachers did not use the textbook as the main source in the classroom teaching process. When the obtained data are examined holistically, it is concluded that even though the rate of pre-service teachers thinking of using the textbook is high, this rate will decrease in professional life.