Automobile assembly workers repeatedly place burdens on their lumbar regions, which can lead to mechanical chronic low back pain. This study aimed to compare the effects of lumbar stabilization exercises performed on a stable or unstable surface on lumbar pain, muscle strength, stability, disability, and depression in patients with chronic low back pain. Twenty-four patients were randomly allocated to a stable or unstable surface group (n = 12 each). Both groups performed each lumbar stabilization exercise for 30 minutes daily five times per week for 6 weeks. Lumbar pain, muscle strength, stability, disability, and depression were assessed before and after intervention. After 6 weeks of training, lumbar pain, stability, disability, and depression improved significantly, whereas muscle strength did not. All post-test values in the unstable surface group improved significantly more than those in the stable surface group. Our findings indicate the more favorable effects of an unstable exercise surface in patients with chronic low back pain. However, further studies are needed to confirm our findings.