A simple and reliable reversed phase HPLC method was developed to determine pharmacologically active compounds ent-continentalic acid, kaurenoic acid, and continentalic acid from the roots of Aralia cordata. Quantitative analysis of diterpenoids of A. cordata were performed by reverse phase C-18 column using a isocratic of acetonitrile : 0.1% trifluoroacetic acid(70:30) with UV detection at 205 nm. The correlation coefficients of each calibration curve of ent-continentalic acid, kaurenoic acid, and continentalic acid were 0.9987, 0.9983, and 0.9986, respectively. The detection limit of ent-continentalic acid, kaurenoic acid, and continentalic acid were $0.5{sim}1.0;{mu}g/mL$, respectively. The contents of ent-continentalic acid (1), kaurenoic acid (2), and continentalic acid (3) of the roots of A. cordata collected from seventeen district markets in Korea were $0.09{sim}0.75;mg/g$, $1.09{sim}5.43;mg/g$, and $2.69{sim}9.08;mg/g$, respectively.