For expansion of forest area by implementing thinning, it is important to analyze attitudes of forest owners, who are the ultimate decision makers for implementation of silvicultural practices in private forests.Using a questionnaire survey, we aimed to clarify the preferences of forest owners for the implementation of thinning practices. We surveyed the attitudes of forest owners regarding silvicultural practices and strategies to expand plantation forest area through commercial thinning.We conducted a questionnaire survey in Hayakawa, Japan, which has a large forest area, to examine forest owner attitudes about implementing precommercial thinning, commercial thinning from below, line thinning, or joint thinning together with other land owners. We also asked forest owners what criteria are important in making decisions for joint implementation of thinning. The interest of forest owners in line thinning was relatively low. Given a harvesting income to expenditure ratio that is not negative, more than half of surveyed forest owners, except for those with no intention to thin, intended to implement thinning. The most important factor for forest owners on whether to agree to joint implementation of thinning was the possibility of reducing harvesting costs by scaling up. If we could provide evidence that harvesting income and expenditure would not be negative when cooperating with other forest owners in joint implementation of thinning, it may be possible to expand managed plantation forest area under thinning with the forest owners’ consent.