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, R 1a and R 1b each independently represent a C 1-6 alkyl group and the like, R 1c represents a hydrogen atom and the like, R 2a , R 2b , R 2c and R 2d each independently represent a hydrogen atom, a halogen atom, a C 1-6 alkyl group and the like, R 3a , R 3b and R 3c each independently represent a hydrogen atom, a halogen atom and the like, and R 3d represents a hydrogen atom and the like.
