A cyclopropane compound represented by the following formula (A) or apharmaceutically acceptable salt thereof has orexin receptor antagonism, andtherefore has apotential use for the treatment of sleep disorder for which orexin receptorantagonism iseffective, for example, insomnia:(see formula A)wherein Q represents -CH- or a nitrogen atom, R1a and R1b each independentlyrepresent a C1-6alkyl group and the like, R1c represents a hydrogen atom and the like, R2a,R2b, R2c and R2d eachindependently represent a hydrogen atom, a halogen atom, a C1-6 alkyl groupand the like, R3a,R3b and R3c each independently represent a hydrogen atom, a halogen atom andthe like, and R3drepresents a hydrogen atom and the like.
