Beneficial effects of forest walking have been reported by previous basic researches. However, practical data about existing health tourisms still remain insufficient. This study aimed at clarifying how the participants' moods change in the course of the forest walking in Kaminoyama. Kaminoyama in Yamagata prefecture is promoting a health tourism connecting the hot spring and forest walking. The questionnaire about mood alteration was conducted three times during rest breaks as well as before and after the walking program. The Questionnaire included a mood scale of 12 items concerning ‘Active mood’, ‘Relaxed mood’ and ‘Negative mood’. To point out the factors of mood changing, the respondents were also asked about their impressive points in the walking program. The results showed that participants' ‘Active mood’ and ‘Relaxed mood’ enhanced and ‘Negative mood’ was mitigated gradually in the course of the walking program. Even on a rainy day ‘Negative mood’ was reduced. It was suggested that participants' moods change is interactively affected not only by natural environments but also by physical characteristics of the trail, information from guides and communication with other participants.