To provide a modifier containing a polymer capable of decreasing surface tension of an organic solvent for coating.

This modifier contains the block copolymer which contains a fluoroaliphatic group-containing monomer expressed by the formula (R0 is H, a halogen or methyl; L is a bivalent bond; A is H or F; m is an integer of 1 to 6; and n is an integer of 1 to 18) as a polymeric unit and further contains fluorine atoms in an amount of ≥3 mass% based on a total mass of the polymer.