The purpose of this study is to evaluate effectness of Tramadol Hydrochloride/Acetaminophen SR Tab. and Tramadol Hydrochloride/Acetaminophen Tab. in patients with low back pain.

Inclusion Criteria:

1. Adult males/Females aged over 20 years
2. Patient with low back pain who needs analgesic administration
3. Patient with low back pain Who correspond with Class 1, 2 in Quebec Task Force Classification
4. Pain VAS Value over 40 mm
5. Subjects who voluntarily or legal guardian agreed with written consent

Exclusion Criteria:

1. Patients with severe GI tract disorder, liver disease, renal disease, heart disease, hypertension
2. Patients with obvious secondary cause(metastatic cancer, fracture, infectious disease)
3. Patients who had taken back surgery within 24 weeks from the screening point
4. Patients who had taken opioid drug, psychotropic drug within 4 weeks from the screening point
5. Patients who had taken steroid drug(oral, injection) within 4 weeks from the screening point