A TGF-β gene expression inhibitor containing a pyrrole-imidazole polyamide having N-methylimidazole unit (hereinafter also referred to as Py), N-methylimidazole unit (hereinafter also referred to as Im) and γ-aminobutyrate unit which can be holded into an U-shaped conformation at the γ-aminobutyrate unit in the minor groove in a double helix region (hereinafter referred to as the target region) containing a complementary chain corresponding to the sequence at the −557 to −536 in the base sequence of a human transforming growth factor β1 (hereinafter also referred to as hTGF-β1) promoter, either as a whole or a part thereof: TAAAGGAGAGCAATTCT-TACAG (SEQ ID NO: 1) wherein a Py/Im pair corresponds to a C-G base pair, an Im/Py pair corresponds to a G-C base pair, and Py/Py pairs correspond respectively to an A-A base pair and a T-A base pair.