To provide a fucoxanthin-containing fat-soluble oil extracted economically in a high yieLd, to provide a method for producing the same, and to provide a method for producing fucoxanthin.

A fucoxanthin-containing fat-soluble oil is substantially perfectly extracted by performing a first step of heat-treating seaweeds of Sargassaceae and a second step of extracting the fat-soluble oil from the seaweeds of Sargassaceae heat-treated in the first step with an organic solvent. Fucoxanthin can be easily purified by passing a fat-soluble oil obtained from seaweeds of Sargassaceae subjected to the above heat treatment, in particular, to immersion in hot water through a chromatographic column packed with silica gel.