The aim of this study was to determine the optimum storage time of flounder and seabream for the preparation of flatfish and sushi. With increasing storage time(0-6 hours) at 4$^{circ}C$, the moisture, -and fat contents of flounder and seabream flatfish decreased while the total number of bacteria increased. Eicosapentaenoic acid and palmitic acid had the highest content in the flatfish fatty acid composition. The pH of flounder and seabream flatfish both decreased at 4 and 3 hours, respectively, and then increased. With increasing storage time, the hardness and cohesiveness decreased, while the springiness, gumminess,-and chewiness initially increased but then decreased. The rigor mortis increased with increasing storage time and the K values of flounder and seabream flatfish both increased at 4 and 3 hours, respectively, and then decreased, whereas ATP contents decreased and then increased. In the sensory evaluation of sushi, the flounder sushi with flatfish stored for 4 hours and the seabream sushi with flatfish stored for 3 hours were found to be the best making condition.