|The concept of “Taking in the atmosphere of a Forest” (shinrin-yoku, in Japanese) was proposed in 1982 by the Japanese Forestry Agency to help people to relax and revitalize their body and soul (therapeutic effect). Previously, the therapeutic effect had been based on only empirical evidence. However, thanks to the rapid improvement of measurement technology and equipment, the government has been scientifically examining the therapeutic effect of forests and using the resulting data for the benefit of the public. The effect is thought to differ depending on the kinds of trees, the spatial structure and the specific atmosphere of the forest environment. Therefore, we decided to study the therapeutic effect of two old-growth forests. As a control, we selected a wellmaintained artificial forest. We measured and compared the therapeutic effect on the subjects, paying attention to 1) their impression of the forest space and 2) how their feeling changed after walking through each forest. Consequently, we found that subjects considered the old-growth forests with huge trees as more sacred, more comfortable, more serene and more natural than the control forest. Moreover, in the control forest there was no difference in any of the indicators used in the survey, while in the old-growth forests the therapeutic effect was confirmed by several indicators.