This experiment was conducted to investigate the quality characteristics and antioxidant activities of ganache added with Porphyra tenera powder(PTP) or Enteromorha Prolifera powder(EPP). The levels of PTP and EPP addition to ganache were 0, 1, 2, 3%. The physicochemical quality characteristics of ganache added with PTP are as follows : The moisture content decreased as the PTP content increased to 1, 2 and 3 %, which was significantly different from the control group. The soluble solid content (°Brix) and reducing sugar content(%) decreased depending on the amount of PTP. The pH decreased as the amount of PTP added increased, whereas the acidity increased as the amount of PTP increased. As a result of the phycocyanin and chlorophyll measurement, ganache containing 3% PTP were significantly highest among the groups. Lightness (L) and Yellowness (b) of ganache decreased with amount of PTP in the Hunter color system. However, redness (a) tended to increase. Textural properties by TPA showed that the hardness of ganache increased with increasing amount of PTP. The cohesiveness, gumminess and chewiness of PTP increased significantly. Springiness was not significantly different from the amount of PTP added. Total phenolics and flavonoid contents in ganache increased with amount of PTP. DPPH radical scavenging activities of ganache increased with increasing PTP. In sensory evaluation results, the overall acceptability score of ganache chocolate containing 1% PTP showed highest among the groups. The color, aroma, and taste were the highest when the amount of PTP added was 1%. The texture was not significantly different according to the amount of PTP added. The intention to purchase was the highest in the group of 1% PTP added as well. These results show that the addition of laver to ganache chocolate makes it possible to manufacture high quality chocolate with high antioxidant activities. The following are the quality characteristics of ganache added with EPP: The moisture content of control was highest and decreased as amount of EPP increased. The soluble solid content (°Brix) and reducing sugar content (%) increased depending on the amount of EPP. Whereas the pH of ganache added with EPP decreased, the acidity increased. As a result of the phycocyanin and chlorophyll of ganache increased with the amount of EPP increased. Lightness (L), Redness (a) and Yellowness (b) of ganache decreased with amount of EPP in the Hunter color system. Textural properties by TPA showed that the hardness, gumminess and chewiness of ganache increased with the amount of EPP increased. Total phenolics and flavonoid contents in ganache increased with amount of EPP. DPPH radical scavenging and SOD-like activities of ganache increased with increasing EPP. In sensory evaluation results, the score of acceptability of 1% added ganache chocolate was the highest among treatments. The score of purchase intention was the highest in the addition of green laver to chocolate is desirable for the preparation of high quality chocolate with high antioxidant activities.