Green space conservation activities in Japan have been supported by citizens’ volunteer work on their off-days; yet these citizens are also aware of the problem that they do not have enough time to spare for conservation activities. In this study, the likelihood of participation in green space conservation activities among these citizens has been uncovered by studying their willingness to work (WTW) in such activities. In addition, based on their preferred participation styles and attitude toward participation, a method to convert their WTW to actual participation has also been identified. An attitude survey was conducted in February 2014 (n=2,000). The subjects were citizens who were interested in participating in green space conservation activities. A question was asked: How many days in a year are you willing to participate in green space conservation activities utilizing your off-days? Preferred participation styles, key factors to participate in conservation activities, and opinions about problems had been also asked in the survey. As a result, the average number of days of WTW among citizens was 11.6 days. Unique characteristics in WTW were detected according to ages and occupation. Respondents who have been recognizing advantages with participation in conservation activities scored higher in WTW.