Abstract: The present invention relates to a pharmaceutical composition comprising an acanthoside B compound as an effective ingredient for preventing or treating dementia or for improving a cognitive function. In the present invention, a desalted glasswort extract, and acanthoside B, which is isolated from the extract and acts as an effective ingredient inhibitory of acetylcholine esterase, were found to have an excellent neuroprotective activity through the inhibition of neuroinflammation and to improve memory retention and remarkably enhance spatial cognitive ability as measured by passive avoidance test and Y-maze test in a scopolamine-induced amnesic animal model. The acanthoside B or glasswort extract of the present invention can be applied to a pharmaceutical composition for preventing or treating dementia, a pharmaceutical composition for improving a cognitive function, or a health functional food or feed for improving memory retention and cognitive function.