Fourteen diterpenes were isolated from the n-hexane fraction of the roots of Aralia cordata (syn. = A. continentalis). Through spectroscopy, the chemical structures were determined as:ent-pimara-8(14),15-diene-19-oic acid (1); ent-kaur-16-en-19-oic-acid (2); 18-nor-ent-pimara-8(14),15-diene-$4{eta}$-ol (3); 18-nor-ent-kaur-16-ene-$4{eta}$-ol (4); ent-pimara-8(14),15-diene-19-ol (5); $7{alpha}$-hydroxy-ent-pimara-8(14),15-diene-19-oic acid (6); $7{eta}$-hydroxy-ent-pimara-8(14),15-diene-19-oic acid (7); ent-pimar-15-en-$8{alpha}$,19-diol (8); 7-oxo-ent-pimara-8(14),15-diene-19-oic acid (9); $16{alpha}$-hydroxy-17-isovaleroyloxy-ent-kauran-19-oic acid (10); 17-hydroxy-ent-kaur-15-en-19-oic acid (11); $15{alpha}$,$16{alpha}$-epoxy-17-hydroxy-ent-kauran-19-oic acid (12); $16{alpha}$,17-dihydroxy-ent-kauran-19-oic acid (13); and $16{alpha}$-methoxy-17-hydroxy-ent-kauran-19-oic acid (14). Compounds 4, 5, 8, 12, and 14 were first isolated from this plant. The anti-Alzheimer and antioxidant effects of ent-pimarane-type diterpenes 1, 3, 5, 8, and 9, as well as ent-kaurane-type diterpenes 2, 4, and 10~13, were evaluated via $eta$-site amyloid precursor protein cleaving enzyme 1 (BACE1), acetylcholinesterase (AChE), butyrylcholinesterase (BChE), peroxynitrite ($ONOO^-$), and nitric oxide ($NO{cdot}$) assays. Of the compounds tested, 8 exerted the most effective BChE inhibition with an $IC_{50}$ value of $7.58;{mu}M$, followed by 3, 13, 11, 2, and 10. Compounds 9~11 exhibited good BACE1 inhibitory activities with $IC_{50}$ values of $18.58{sim}24.10;{mu}M$. However, 11 showed marginal AChE inhibitory effect, and all compounds tested showed no scavenging activities on $ONOO^-$ and $NO{cdot}$ at a concentration of $100;{mu}M$.