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Microwave cure was used for the quick curing process of fly ash (FA) geopolymer fabrication for heavy metal immobilization purposes. The geopolymers synthesized by microwave cure were applied for heavy metal immobilization of Pb ion in the matrix. Fly ash was raw material and alkaline activator of sodium silicate and sodium hydroxide (NaOH) solution were fixed at mass ratio of 2.5 for geopolymerization. 0.5 wt% Pb(NO3)2 was added to the geopolymer pastes precured at 30 °C for 2 h for carrying out dense structured geopolymers. Also, porous formed geopolymer was obtained under microwave irradiation at 300 and 700 W for 1 min exposure. The effect of geopolymer matrix on microwave irradiation power, NaOH concentration, and precuring combination before was examined to be optimized in the immobilization efficiency of Pb ion. The immobilization efficiency depended on the dense degree of geopolymer having higher compressive strength as prepared at the 300 W microwave radiation for dense bulks. In addition, higher NaOH concentration also enhanced these abilities. However, higher microwave power at 700 W decreased compressive strength and immobilization efficiency.