Various information on the geochemical characteristics of seawater is recorded in reef-building coral skeletons, which have been widely utilized for the high temporal resolution (one or two weeks) analysis of paleoenvironment in the tropical ocean. The stable oxygen/carbon isotopic ratios and trace element contents in coral skeletons are generally applied to the paleoenvironmental reconstruction. The paleoenvironmental analysis based on organic matter in coral skeletons, however, has rarely been performed. Organic analysis of coral skeletons has been conducted mainly for the understanding of coral biomineralization. Coral organic matter, which is much less reactive than sedimentary organic matter, can be a useful paleoenvironmental proxy. Combination of organic and inorganic geochemical analyses for coral skeletons will be a powerful tool to provide more information on the paleoenvironment.