The aim of this study is to investigate the effect of using the interactive whiteboard in mathematics teaching process on the 7th-grade students' achievement. This study was conducted as experimental design. Experimental and control groups were composed of 58 7th-grade students from one school in the 2015-2016 educational year in Ankara. As a measurement tool, an achievement test developed by the researchers was used as the pre-test and post-test. An education program which included the activities with the interactive whiteboard was developed by researchers. And, this program was implemented to the experimental group 12 hours over 3 weeks. On the other hand, activities for the control group were limited to the blackboard usage. In the analysis of the data, "analysis of covariance (ANCOVA)" was used by defining the pre-test scores as "covariate" variable. According to the findings, it was observed that there was a significant difference between experimental and control groups pre-test average scores. When the difference of pre-test scores under control, it was observed the significant difference between the average post-test scores in favor of the experimental group. These findings show that using the interactive whiteboard in mathematics teaching process has positive effects on the students' mathematical achievement. These results are supported by some other researchers' findings.