The thermal stability increase of a-amylase obtained from locale bacteria isolate Bacillus subtilis ITBCCB148 was achieved by immobilization process using an ionic exchange matrix of DEAE-Cellulose. The result showed that the immobilized enzyme has an optimum temperature of 60°C; KM 14.8 mL substrate and V_max 42.4 U/mL. The thermal stability storage temperature of 60°C, pH 9.0 and 60 minutes demonstrated the immobilized enzyme has residual activity of 28.1%; k_i = 0.0224 min.^-1; and ΔG_i = 103.7 kJ mol^-1. Although the immobilized enzyme’s thermal stability was only increased 1.5 times, at higher temperatures, it was much more stable than the native enzyme.