It is quite difficult to analyse the profit that can be obtained from tree plantations because very many factors are involved. However, for giving sound guidelines to forestry enterprices, it is beneficial in calculating the cost ratios. The present author has made some predetermined assumptions for this calculation relating to larch plantations. According to the results, to insure a sound enterprice, the rate of the annual compound interest should be less than 8 percent taking into consideration the risk ratio. It is true, however, that we do not always depend only upon profit analysis results in forest management.