The molecular chaperone heat shock protein 90 (Hsp90) is responsible for maintaining the correct folding and stability of many signaling proteins. It is a promising target of cancer therapeutics and several other diseases, including neurodegenerative disease, nerve injuries, inflammation, and infection. In an effort to identify new Hsp90 inhibitors from natural sources using an in vitro ATPase inhibition assay, two 6-alkylsalicylic acid analogues, salaceyin A and B were identified from the culture extract of Streptomyces. Salaceyin A and B exhibited moderate ATPase inhibitory activities with $IC_{50}$ values of 68.3 and 65.2 ${mu}M$, respectively. Binding of salaceyins to human $Hsp90{alpha}$ was examined by competition binding experiments with ATPSepharose beads. However, the compounds exhibited no degradation activity of Hsp90 client proteins, Her2, c-Raf, or Akt.