This study is aimed at determining the effects of rehabilitation training on lumbar extension strength and relief of back pain in middle-aged women of low back pain. Twenty-nine subjects(total 29 people; CLBP 16, HLD 13) were trained twice per week for eight weeks and completed a maximum isometric test at various flexion angle(the degree of $0^{circ}$, $12^{circ}$, $24^{circ}$, $36^{icrc}$, $48^{circ}$, $60^{circ}$, $72^{circ}$) by lumbar extension machine. The result showed that. 1. Patient group of CLBP were increased the maximum lumbar extension strength at a range of 7 flexion angles after rehabilitation rather than no rehabilitation(on the average 60.75%). The operated patient group in HLD also showed an increase of 56.55%. In view of these cases, all of two groups showed a significant increase of muscle strength(p<.05). But there is no difference between pre-exercise and post-exercise groups. 2. Patient group of CLBP were increased higher rate than 41% for maximum lumbar extension strength(91.79% at $0^{circ}$, 79.41% at $12^{circ}$, 65.89% at $24^{circ}$) at all angles after 8 weeks training. Both groups indicated a significant increase(p<.05) of lumbar extension strength at all degrees. There is no difference between pre-exercise and post-exercise groups. 3. Relief of back pain in Patient group of CLBP showed a decrease of average 105.2% and patient group of HLD indicated a decrease of average 64.57% two groups showed a significant reduction (p<.05, p<.05). But in case of a decrease of pain, CLBP group got 3.44 points and HLD group got 4.77 points. In view of these results, two groups showed remarkable reduction of back pain, however HLD group had residual pain relatively.