Provided is a method for detecting a stem cell based on an undifferentiated sugar chain marker having a specific sugar chain structure, wherein the stem cell is detected by detecting podocalyxin contained in a culture supernatant or a lysate of cells by a “lectin-antibody sandwich method” using a combination of a lectin and an antibody and having high sensitivity, the method including steps of: contacting the culture supernatant or the lysate, a lectin capable of binding to a sugar chain represented by (Formula 1) or (Formula 2), and an antibody capable of binding to keratan sulfate to form a complex composed of the lectin, podocalyxin and the antibody; and detecting the complex. wherein R1 represents an OH group or any sugar chain and R2 represents an OH group or any sugar chain, protein, lipid, or another molecule. wherein R1 represents an OH group or any sugar chain and R2 represents an OH group or any sugar chain, protein, lipid, or another molecule.