Two new biphenyl ether lignans, named obovatol (1) and obovatal (2) were isolated from the leaves of Magnolia obovata THUNB. (Magnoliaceae) and their chemical structures were determined to be 4', 5-diallyl-2, 3-dihydroxybiphenyl ether and 3, 4-dihydroxy-5-(pallylphenoxy) cinnamic aldehyde by means of chemical and spectral studies. The former substance showed antibacterial activity against a cariogenic bacterium, Streptococcus mutans, but was less active than magnolol (5) and honokiol (6).