The objectives of this study were to prepare itraconazole (ITZ) nanoparticles using a Shirasu porous glass (SPG) membrane and to characterize the effects of diverse preparation parameters on the physical stability of nanoparticles. SPG membrane technology was used for the antisolvent precipitation method. The preparation of nanoparticles was carried out over a wide range of continuous-phase factors (type of surfactant, surfactant concentration), dispersed-phase factors (solvent type, solvent volume used to dissolve ITZ), and technical factors (pressure, membrane pore size, stirring speed in the continuous phase, temperature). Improved physical stability of nanoparticles was observed when surfactant with a lower molecular weight and higher hydrophilic segment ratio was used. The water miscibility of the solvent also had an effect on the physical stability. N,N-Dimethylacetamide contributed to creating a well-rounded shape and narrow size distribution due to high miscibility. Concentration of the surfactant and solvent volume used for dissolving ITZ were related to instability of nanoparticles, resulting from depletion attraction and Ostwald ripening. In addition to these factors, technical factors changed the environment surrounding ITZ nanoparticles, such as the physicochemical equilibrium between surfactant and ITZ nanoparticles. Therefore, the appropriate continuous-phase factors, dispersed-phase factors, and technical factors should be maintained for stabilizing ITZ nanoparticles.