In order to effectively utilize marine processing by-product such as fish scale, chemical compositions for the scale were analyzed. The selected fishes were gray mullet, Mugil cephalus, living in the sea and carp, Cyprinus carpio in the fresh water, having a lot of scales among the fishes living in seawater and fresh water. And we also investigated the difference in the chemical compositions between gray mullet and carp, depending on both living circumstances. The major components of the scales were found to be crude ash and crude protein which were each about 49% for gray mullet and which were about 20% and 79% for carp, respectively, on the basis of dried scales. The proteins extracted from both scales proved to be collagen through amino acid compositions and SDS polyacrylamide gel electrophoretic patterm. Also this scale collagen was assumed to by Type I collagen because the migration rate of $alpha$1 and $alpha$2 subunit of the collagen were almost the same those as calf skin Type I collagen. Most of proteins from gray mullet was collagen, however, the collagen content in proteins from carp was estimated to be only about 53%, on the basis of the ratio of hydroxyproline to protein. The crude ashes of both scales identified to be hydroxyapatite through element compositions and X-ray diffraction analysis. In conclusion, both fishes in different living circumstances were almost similar to in the chemical compositions but chemical contents for crude ash and crude protein.