The present study was designed to examine the stages of exercise behavior, their changes and related factors in older adults. The data were obtained through questionnaires distributed to 842 (362 males, 480 females) older adults. ANOVA was applied for data analysis. The main findings were as follows : (1) Subjects were classified into six groups : precontemplation (PC) (27.1%), contemplation (C) (13.3%), preparation (P) (22.9%), action (A) (2.8%), maintenance (M) (27.6%), and pause (PA) (6.4%) in males, and PC (40.2%), C (13.3%), P (16.5%), A (1.0%), M (17.9%), and PA (11.0%) in females. (2) Seven factors (exercise self-efficacy, perceived benefits of exercise (Pros), perceived barriers of exercise (Cons), ADL, positive social support from family (family PSS), negative social support from family (family NSS), and positive social support from friends (friends PSS) significantly affected the scores for the stages of exercise behavior. Exercise self-efficacy results showed a steady and significant increase from PC to M. Perceived benefits of exercise and ADL scores were significantly higher for subjects in M compared to A, P, PA, C, PC and M, A, P, PA, C compared to PC. Perceived barriers of exercise and family NSS scores were significantly lower for subjects in M compared to PC. Family PSS and friends PSS scores were significantly higher for subjects in M compared to PC. Interventions based on the stage of exercise behavior change could be effective. Different kinds of intervention strategy using the elements of "Decisional balance", "Social support", "ADL", and "Exercise self-efficacy" would be useful at each stage.