An object of the present invention is to provide a protein useful as a sphingomyelin detecting probe, which specifically recognizes sphingomyelin and has low cytotoxicity. The present invention provides a protein which has an amino acid sequence having, as the amino acid sequence from the 1st to the 48th amino acid, the amino acid sequence from the 1st to the 48th amino acid in Lysenin 1, and as the amino acid sequence from the 49th to the 298th amino acid, the amino acid sequence from the 51st to the 300th amino acid in Lysenin 3; and a protein which is obtained by deleting N terminal and/or C terminal from earthworm toxins Lysenin 1 or 3, and which specifically recognizes sphingomyelin.