To understand influence of climate change on mature Cryptomeria japonica trees, we examined physiological and morphological responses of C. japonica leaves to artificial soil drought induced by rainfall exclusion experiment. We constructed a roof in a 40-year-old C. japonica stand to exclude throughfall (treatment plot, 10×10 m) and started the experiment since mid-May, 2018. We measured leaf water potential almost every week until January and diurnal changes in leaf gas exchange characteristics twice. Length of current shoots was monthly measured. Soil water potential in the treatment plot substantially decreased and intermittently reached to −0.4 MPa at soil surface. However, there was no difference in leaf water potential between the treatment and control plots throughout the experimental period. On a sunny day in July, stomatal conductance (g_s) was almost identical between the plots during the morning, however midday depression was slightly larger in the treatment tree. In October, g_s in the treatment tree was lower compared with the control tree throughout the day. Morphologically, the current shoot length was significantly shorter in the treatment plot than in the control plot. These results suggest that C. japonica trees may decrease water consumption by stomatal adjustment and leaf mass reduction in response to soil drought.