This study consist of treatment phase (12 weeks) and extension phase (40 weeks). This study is a multicenter, open-label, uncontrolled, multiple ascending dose (MAD) study to evaluate mainly the safety and tolerability of 12-week repeated subcutaneous administration of E6011 in Japanese subjects with Rheumatoid Arthritis. First 12 subjects will enroll as 100 mg group, next 12 subjects will enroll as 200 mg group, and last 9 subjects will enroll as 400 mg group. A total of 33 subjects will receive repeated subcutaneous administration of E6011. Subjects who roll over onto the Extension phase will have continued monitoring until 52 weeks after the initial administration.