As the results of intensive studies aiming at developing a remedy which has an effect of promoting osteogenesis by accelerating the function of osteoblasts, it is found out that specific nitrogen-containing heterocyclic compounds show a potent effect of promoting osteogenesis by osteoblasts and thus are useful as excellent preventives or remedies for metabolic bone diseases. Namely, it is intended to provide 3,6-disubstituted-1,2,4-triazo[4,3-b]pyridazine compounds having an effect of promoting osteogenesis or pharmaceutically acceptable salts thereof, and medicinal compositions, in particular, osteogenesis promoters comprising these compounds with a pharmaceutically acceptable carrier.