This clinical study is scheduled to be performed for the purpose of evaluating the safety and effectiveness of golimumab (CNTO148) administered in combination with stable dose (6-8mg/week) of methotrexate (MTX) to patients with rheumatoid arthritis (RA). CNTO148 50 mg group: CNTO148 50 mg SC injections every 4 weeks from the first administration until week 152. If early escape, 100 mg SC injections every 4 weeks from week 16 until week 152. CNTO148 100 mg group: CNTO148 100 mg SC injections every 4 weeks from the first administration until week 152 whether early escape or not Placebo group: Placebo SC injections every 4 weeks from the first administration until week 20 and then CNTO148 50mg SC injections every 4 weeks from week 16 until week 152