The purpose of the present invention is to provide a novel indazole compound which is capable of inhibiting HSP90 and has a cytostatic effect. Another purpose of the present invention is to provide a drug useful for preventing and/or treating, on the basis of an HSP90 inhibitory effect, a disease in which HSP90 participates, in particular, cancer. A compound represented by general formula (I) or a salt thereof [in formula (I), X, Y1 to Y4, A, B and R1 to R8 are each as defined in claims of the present application].本發明提供一種具有HSP90抑制作用,且具有癌細胞增殖抑制效果的新穎之吲唑化合物。另外,本發明提供一種基於HSP90抑制作用,而可用於預防及/或治療該HSP90參與之疾病、尤其是癌的醫藥。本發明係下述通式(I)所表示之化合物或其鹽:(式中,X表示CH或N;Y1、Y2、Y3及Y4中任意1個或2個為C-R3或N,其餘表示CH;A及B相同或不同地表示可具有取代基的具有選自N、S及O中之1~4個雜原子的單環性之不飽和雜環基;R1表示氫原子、可具有取代基之碳數1~6之烷基等基;R2表示氫原子、鹵素原子等;R3表示氫原子、鹵素原子等;R4及R5相同或不同地表示羥基等;R6及R7相同或不同地表示氫原子、碳數1~6之烷基等;R8表示可具有取代基之碳數3~7之環烷基等)
