This study examined the effect of the use of Concept Mapping on female students' achievement in geography at the preparatory level. The study targeted the first unit of the textbook entitled "Population'. The study sample was two third preparatory classes from Al-Amal Basic Education School in Barka randomly chosen by the Directorate General of Education, Al-Batinah South. This sample was divided into two group( experimental and control groups). The former consisted of 40 students and the later 41. The two groups were found similar in terms of overall performance based on their general results in the previous class, second preparatory. To measure the achievement of the unit the researcher built an achievement test consisted of 25 items testing various cognitive skills and obtained it after the study The result of the study shown the existence of significant difference at level (a = 0.05) in mean achievement between the experimental and the control group in favor of the experimental group. There were also The significant difference at level (a = 0.05) in mean achievement between the experimental and the control group in knowledge, comprehension and application levels between the experimental and the control group in favor of the experimental group. According to the results of the study, the researcher offered many recommendations related curriculum and methodology as well as pointing out the need for more researche in the field of concept mapping.