(wherein R1, R2 and R3 are the same or different, and represent a hydrogen atom, lower alkyl, lower alkenyl or lower alkynyl; R4 represents cycloalkyl, —(CH2)n—R5 or a group represented by the above formula (II); and X1 and X2 are the same or different, and represent an oxygen atom or a sulfur atom) The present invention provides, for example, agents for treating migraine comprising, as an active ingredient, a xanthine derivative represented by the above formula (I) or a pharmaceutically acceptable salt thereof.