This study examined the inhibitory activity of Ecklonia cava (EC) against ${alpha}$-amylase to evaluate the availability of EC extract as a functional food agent. To verify the inhibitory activity of EC against porcine pancreatic ${alpha}$-amylase, potato starch was used as a substrate. This analysis revealed that EC ethanol extract exhibited high ${alpha}$-amylase inhibitory activity. For potential application within the food industry, the stability of the activity of EC ethanol extract under various heat and pH conditions was examined. The ${alpha}$-amylase inhibitory activity of EC ethanol extract was not affected by the heat and pH treatment conditions used in this study. These results suggest that EC has the potential for development as a functional food agent.