PURPOSE: To obtain zeolite having a uniform crystal structure and suitable for use as a catalyst or the like by subjecting an aqueous mixture contg. a silica source, an alumina source and an alkali metallic source to a hydrothermal reaction in an autoclave contg. a lower hydrocarbon in the vapor phase part.

CONSTITUTION: A silica source such as siica gel or sodium silicate, an alumina source such as sodium aluminate or aluminum sulfate, and an alkali metallic source such as NaOH or KOH are added to water to prepare an aqueous mixture having about 5W1,000 molar ratio of SiO2/Al2O3, about 5W200 molar ratio of H2O/SiO2 and about 0.01W1 molar ratio of OH-/SiO2. The mixture is charged into an autoclave, a gaseous lower hydrocarbon such as methane or propane is introduced into the space in the autoclave, and after tightly sealing the autoclave, the mixture is subjected to a hydrothermal reaction at about 100W300°C for about 6W800hr to obtain desired zeolite.