Inclusion complex of omeprazole(OMZ) with hydroxypropyl-$eta$-cyclodextrin(HP-$eta$-CD) was prepared by freeze-drying method. The complexation was confirmed by means of UV, CD, IR, DSC, XRD and $^{1}$H-NMR spectra. The benzimidazole moiety of OMZ might be found to be included into the cavity of HP-$eta$-CD and the inclusion complex appeared to be $A_{L}$ type. The stoichiometric ratio of OMZ : HP-$eta$-CD was found to be 1:1, and the stability constants of the inclusion complex by solubility and UV method were about 34 and 45 M$^{-1}$, respectively. The dissolution of OMZ was significantly enhanced from powder and. yablet of OMZ-HP-$eta$-CD complex when compared to those of OMZ alone, and oil-to-water partition coefficient of OMZ-HP-$eta$-CD complex was significantly higher than that of OMZ alone. Therefore, it was expected that the bioavailability of OMZ could be improved markedly by inclusion complexation of OMZ with HP-$eta$-CD.