ARID1A is one of the important cancer-related genes and regulates transcription of certain genes by altering chromatin structure. Inactivated mutations and decreased expression of ARID1A gene have been reported in several kinds of cancer. Histone H2B is a major component of chromatin and encoded by HIST1H2BE. The goal of the study is to evaluate expressing status of ARID1A and H2B as well as their correlation on breast cancer. Gene expression profiles of ARID1A and H2B on Oncomine database are analyzed. Tissue microarray of breast cancer was used for examination of ARID1A and H2B expression by immunohistochemistry. As a result, the disagreement of ARID1A expression was found, while HIST1H2BE expression is elevated in 4 out of 5 datasets on Oncomine database. There were 15 cases (20%) of breast cancers that were positive for ARID1A. Fifty-eight out of 75 cases of breast cancer (77.3%) were highly expressed for H2B protein and 17 cases (22.7%) were low expressed for H2B protein. All cases with ARID1A expression are overlapped with H2B high expression. Among 15 cases with ARID1A and H2B coexpression, 13 are invasive ductal carcinoma and 2 are mucinous carcinoma. Our results indicate that ARID1A gene may be involved in carcinogenesis of some subtypes of breast cancer.