Provided is a polypeptide that binds specifically to an artificial low molecular weight ligand. This polypeptide, in which a BC loop of a
fibronectin type III domain
scaffold contains an
amino acid sequence represented by the following formula (1): X1aX1bX1cX1dX1eDX1fX1gD (wherein X1a is A, S, or R, X1b and X1c are each independently an arbitrary
amino acid, X1d is N, H, W, or Y, and X1e to X1g are each independently an arbitrary
amino acid), and an FG loop contains an amino acid sequence represented by the following formula (2): X2aX2bX2cX2dX2eKX2fX2gX2hX2i (wherein X2a and X2b are each independently an arbitrary amino acid, X2c is G, M, N, Y, or W, X2d is an arbitrary amino acid, X2e is Y, F, P, W, V, or A, X2f is W, Y, V, F, or S, X2g is W, L, V, or M, X2g if V, C, G, or A, and X2i is an arbitrary amino acid), binds specifically to an artificial low molecular weight ligand such as 1-(4-hydroxyphenyl)-3-phenylurea (HPPU) or a derivative thereof.