Recently, several mutant laver Pyropia yezoensis strains were developed. In this study, control laver Pyropia yezoensis and its mutant Py500G were compared for their amino acid contents and antioxidative activities. There was no significant difference of total amino acid contents between wild-type and mutant Py500G, but mutant had higher free amino acid contents than wild-type. Also, total phenolic content was higher in mutant Py500G. Phycoerythrin and phycocyanin contents were higher in wild-type. But, antixoidative activities were shown to be higher in mutant Py500G. These results will be useful for the development of new cultivar of Pyropia.