PROBLEM TO BE SOLVED: To provide a medicine which can be used as a preventive or therapeutic agent of arthrosis, and the like.SOLUTION: A coumarin derivative or a pharmaceutically acceptable salt or hydrate thereof which is an active ingredient of the present invention exhibits excellent cartilage destructive inhibitory action, synovial cell growth inhibition action, and inhibitory effect of increased gene expression in a pharmacological test using isolation of sulfated glycosaminoglycans (sGAG) or proliferation of synovial cells or gene expression of cartilage matrix decomposition associated factors as an indicator or exhibits an excellent effect on osteoarthritis or rheumatoid arthritis in animal experiments using the model animal of osteoarthritis or rheumatoid arthritis. Thus, the medicine of the invention is very useful as an active ingredient of pharmaceutical compositions for the preventive or therapeutic agent of arthrosis such as osteoarthritis and rheumatoid arthritis and the like.
