As a rapid and quick bioactive compound evaluation technique, we utilized an automatic system of high throughput screening (HTS) to investigate ${alpha}$-glucosidase inhibitory efficacy of seaweeds, collected from Jeju Island in Korea. In this study, different extracts with methanol at $20^{circ}C$ and $70^{circ}C$ from 23 species of brown seaweeds and 22 species of red seaweeds and 9 species of green seaweeds were subjected to HTS. Of the brown seaweeds tested, Myelophycus simplex (20B3), Ishige sinicola (20B5, 70B5), Colpomenia sinuosa, (20B14, 70B14), Hizikia fusiforme (20B21), Ishige okamurai (70B22) and Ecklonia cava (70B23) showed significantly high ${alpha}$-glucosidase inhibitory activity with 96.52%, 98.34%, 98.37%, 80.49%, 96.16%, 76.32%, 98.32% and 98.12%. Schizymenia dubyi (20R15), Gelidium amansii (20R16) and Polysiphonia japonica (70R22) amomng the red seaweeds showed remarkable ${alpha}$-glucosidase inhibitory activity more than 95%. On the other hand, the green seaweeds showed poor ${alpha}$-glucosidase inhibitory activities (less the10%) at 1 mg/ml.