An evaluation of transpiration is required for applications in agricultural and environmental management because crop yields and plant growth are primarily water limited. This study was aimed to determine the transpiration of Cnidium officinale using weighing lysimeter and to evaluate the relationship between transpiration and meteorological factors such as solar radiation, air temperature, etc., Transpiration was increased as the leaf area increased with the growth stage. Also daily transpiration per unit leaf area was 0.69±0.16 g cm-2 day-1 and there was no significant difference during cultivation period. The maximum transpiration was 620.6 g m-2 hour-1 and diurnal changes of transpiration was highly correlated with solar radiation although the maximum transpiration was observed at 20~26℃ air temperature. The ratio of carbon accumulation to transpiration was 0.12%. Our result shows that transpiration of Cnidium officinale seem to be mainly governed by solar radiation energy in clear days and 97% of the water is discharged through transpiration for the heat dissipation. Therefore, weighing lysimeter can be used to measure transpiration accurately and may be useful in interpreting the plant growth.