Inclusion complex formation of furosemide with ${eta}-cyclodextrin({eta}-CyD)$ in solid state was confirmed by X-ray diffractometry, IR spectroscopy and differential scanning calorimetry (DSC). The solid complexes of ${eta}-CyD$ with furosemide in molar ratio of 2 : 1 were prepared by solvent evaporation method. The photodegradation of furosemide in alkaline solution under the light and the hydrolysis of furosemide in acidic solution were not inhibited by complex formation with ${eta}-CyD$. However, the bioavailability of furosemide was improved by complex formation with ${eta}-CyD$ after oral administration to rats.