Abstract: With the object of providing a novel anti-hallucination agent capable of suppressing, treating or preventing a hallucinatory symptom, the anti-hallucination agent of the invention contains an Atractylodes-derived crude drug as an active ingredient or contains a compound represented by the following formula (Ia), a stereoisomer thereof or a salt thereof as an active ingredient: in the formula, the double lines consisting of a solid line and a broken line represent a single bond or a double bond; R1 represents a hydrogen atom or a hydroxyl group, with the proviso that R1 does not exist when the carbon atom to which R1 is attached is linked to one of the neighboring carbon atoms through a double bond; R2 represents a hydrogen atom or is combined with R3 to represent a cyclic group which may have a substituent; and R3 represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms which may have a substituent or is combined with R2 to represent a cyclic group which may have a substituent.