A cyclopropane compound represented by the following formula (A) or a pharmaceutically acceptable salt thereof has orexin receptor antagonism, and therefore has a potencial of usefulness for the treatment of sleep disorder for which orexin receptor antagonism is effective, for example, insomnia:wherein Q represents —CH— or a nitrogen atom, R1a and R1b each independently represent a C1-6 alkyl group and the like, R1c represents a hydrogen atom and the like, R2a, R2b, R2c and R2d each independently represent a hydrogen atom, a halogen atom, a C1-6 alkyl group and the like, R3a, R3b and R3c each independently represent a hydrogen atom, a halogen atom and the like, and R3d represents a hydrogen atom and the like.
