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; R
1
represents a hydrogen atom or a hydroxyl group, with the proviso that R
1
does not exist when the carbon atom to which R
1
is attached is linked to one of the neighboring carbon atoms through a double bond; R
2
represents a hydrogen atom or is combined with R
3
to represent a cyclic group which may have a substituent; and R
3
represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms which may have a substituent or is combined with R
2
to represent a cyclic group which may have a substituent.