The present invention provides novel angiogenesis inhibitors effective, safe and highly practical for inhibition of angiogenesis in various diseases, and a method for screening the same. The active ingredients of the angiogenesis inhibitors of the present invention comprise ansamycin antibiotics such as rifampicin, rifamycin SV and 3-formyl rifamycin, which have long been used extensively as antibacterial agents for treating tuberculosis or Gram-positive bacterial infections. The active ingredients of the present invention have excellent angiogenesis-inhibiting activity. The angiogenesis inhibitor of the present invention is effective for inhibition of angiogenesis in malignant tumors, diabetic retinopathy, retinal angiogenesis, inflammatory diseases, and angiogenesis accompanying cardiovascular remodeling, etc., and can be used as therapeutic agents against each disease, etc. Further, the screening method of the present invention makes it possible to perform an effective screening of angiogenesis-inhibiting substances by detecting angiogenesis-inhibiting signals based on gene expression levels.