The species composition and seasonal occurrence of the marine macroalgae on the central coast of Hiroshima Prefecture, specifically in the vicinity of Takehara, in the Seto Inland Sea of Japan were studied. A total of 143 species was identified including 18 species of Chlorophyceae, 43 species of Phaeophyceae, and 82 species of Rhodophyceae. Most species were seasonal and more abundant from February to July, when more than 60 species occurred in each month. March had 79 species, the highest species number in a single month. Ulva pertusa, Codium fragile, Ishige okamurae, Ecklonia kurome, Sargassum fusiforme, S. thunbergii, Corallina pilulifera, and Chondrus giganteus were found throughout the year. Of 143 species, Dictyota linearis, Sporochnus radiciformis, and Martensia fragilis were warm temperate species that reported in the Bungo-channel regions, while only Dictyota linearis can be found in the southern islands of subtropical Japan. The rest of the species were temperate species. There are 104 species commonly found on the coasts of Hiroshima Prefecture, representing the major algal communities along the coast of the Prefecture.