Japan is markedly the most aged country among developed countries and there are many elderly men who don't participate in any community activity in spite of their intention. The aim of this study was to find factors to promote their participation and to confirm the structure of the factors using the grounded theory approach (GTA). We conducted interviews with 43 elderlies of 10 community groups who engaged in crime prevention activities and maintenance/management of local infrastructure in their communities. As a result, ‘incorporating community activities in daily life’ was identified as the core category. The other categories, including ‘realizing secondary effect’ and ‘balancing workload and capacity,’ were structured around the core category and three patterns leading to ‘habitual participation’ were found. Based on these results, methods with which local governments, specialists and community groups promote elderly men's participation were discussed.