Provided is a method for producing a natural red pigment, particularly a plant-based red pigment. The method involves producing a red pigment by reacting a protein hydrolysis product with an iridoid compound having a carboxyl group at position 4 of an iridoid skeleton. The protein hydrolysis product has an amino acid content of at least 35 wt% in terms of the protein hydrolysis product dry weight, and according to ninhydrin assay, at least 50 wt% of the amino acid is glutamic acid and aspartic acid and the ratio of the leucine weight to the total weight of the glutamic acid and aspartic acid is no greater than 8 wt%. It is also possible to react the protein hydrolysis product and taurine or a taurine-containing substance with the iridoid compound.本發明的目的在於提供一種來源於天然物、特別是來源於植物的紅色素的製造方法。本發明提供一種使在環烯醚萜苷骨架的4位上具有羧基的環烯醚萜苷化合物與蛋白質水解物反應來製造紅色素的方法。該方法的特徵在於：在所述蛋白質水解物中，相對於該水解物的乾燥重量的氨基酸含量為35重量%以上；以及利用茚三酮法進行測定時，所述氨基酸中50重量%以上為谷氨酸及天冬氨酸，且亮氨酸的重量相對於所述谷氨酸與天冬氨酸的合計重量的比例為8%以下。也可以使牛磺酸或含牛磺酸的物質和所述蛋白質水解物一起與所述環烯醚萜苷化合物反應。
