To enhance the solubility and stability of lansoprazole (LAN), new proton pump inhibitor, we were prepared various molar ratio of inclusion complex with $2-hydroxypropyl-{eta}-cyclodextrin$ (HPCD) and organic alkali agent, meglumine (MEG). Inclusion complex formation of LAN with HPCD was investigated by Differential Scanning Calorimetry and X-ray diffractometry. The aqueous solubilities of inclusion complexes, and the stabilities of 1:4 and 1:5 inclusion complexes in aqueous solutions containing different concentrations of MEG were examined. The stability of 1:5 LAN-HPCD inclusion complex containing MEG, which was equaled to amount of LAN, was performed in 0.9% NaCl and 5% dextrose solution. The formation of inclusion complex of LAN with HPCD was $A_L$ type and the molar ratio of complex was 1:1. The stability constant was $41.557;M^{-1}$. As molar ratio of LAN to HPCD was increased, solubility of inclusion complex was increased. 1:5 LAN-HPCD inclusion complex was more stable than 1:4 LAN-HPCD inclusion complex. And as contained MEG amount in LAN solution was increased, stability of 1:4 and 1:5 LAN-HPCD inclusion complexes was improved. Also stability of 1:5 LAN-HPCD-MEG inclusion complex in 0.9% NaCl solution and 5% dextrose solution was similar to it in water at room temperature, but it was unstable at $40^{circ}C$.