This study aimed to clarify 1) the changes in the psychological and social ability of participants through short-term nature activities, and 2) the relationship between psychological and social ability and the contents of experiences in nature activities. A questionnaire was administered to 74 elementary students who participated in short-term nature activities. The major findings were: 1) Psychological and social ability improved, with partial exceptions, through short-term nature activities, and 2) The contents of the experiences such as challenges, achievements, and cooperation with other children showed a positive association with the changes in psychological and social ability. These results indicate that short-term nature activities for children have a positive effect on the improvement of Ikiru Chikara (Zest for Living).