On the assumption that water influences the stem growth(volume increase) the three-dimensionally, thickening growth increment of standing Japanese cedars were associated with the values calculated by raising the accumulation quantity of sap flow rate to the one-third. The results showed a close relationship between the values. Roiko-Jokela's relation was applied to mathematically represent the stem morphology by an approximate expression. And the relational expression obtained was integrated to determine the volume of the standing tree. Based on the increased volume(June to July), bulk density, and total sap flow rate(June to July) of the test cedars the sap flow rate requirement for the thickening growth from April to July was calculated to be 470.7(gH_2O/g) per dry weight growth of 1 g. Likewise, the sap flow rate requirement for elongation growth(March to May) was calculated to be276.9(gH_2O/g) per dry weight growth of 1 g. Consequently, it was suggested that elongation growth utilized sap flow rate at a 1.7 times higher efficiency than thickeinng growth.