Breast cancer is prevalent among women and develops from breast tissue. Early diagnosis and accurate treatment is vital to increase the rate of survival. Identification of genetic factors with microarray technology can make significant contributions to diagnosis and treatment process. In this study, several machine learning algorithms are used for Diagnosis of Breast Cancer and their classification performances are compared with each other. In addition, the active genes in breast cancer are identified by attribute selection methods and the conducted study show success rate 90,72 % with 139 feature.