Scoria, which is abundantly found in Cheju island, was used for synthesizing zeolites. Cheju scoria was treated with NaOH at different concentrations, and various times and temperatures of crystallization. SEM, EDX and XRD techniques were empolyed to characterize the synthesized products. SOD, JBW, ANA and CAN phases were identified under various experimental conditions. The results show that plagioclase, the major component of Cheju scoria, could be easily converted to zeolite phases.