To provide a novel inflammasome inhibitor capable of inhibiting activation of inflammasome, the present inventors newly found that arctigenin reduces the amount of 1L-1² released and the amount of activated caspase-1 upon stimulation with ATP, palmitic acid, MSU and Poly(dA:dT) and thus has aneffect of inhibiting inflammasome activation. The present invention provides an inhibitor of inflammasome activation that comprises arctigenin as an active ingredient.