NEW MATERIAL:The fluorine-containing bisphenol derivative of formula I [AO is oxyethylene or oxypropylene; at least one of R1 to R4 is group of formula II, formula III or formula IV (n is 6-9) and the others are H; R' and R" are H, CH3 or CX3 (X is halogen) ; R"' is H, halogen or 1-4C alkyl; m1 and m2 are 0, 1 or 2; a+b+c+d is 2-50].

EXAMPLE: The compound of formula V (a+b+c+d:40).

USE: A surface-modifying agent, etc., having practically sufficient oil-solubility and excellent properties such as chemical resistance, weather resistance, stain- proofness and flame-retardancy.

PREPARATION: The compound of formula I can be produced e.g. by subjecting a bisphenol of formula (a) and a phenol of formula (b) to formalin condensation under acidic condition, adding ethylene oxide or propylene oxide to the resultant novolak compound and substituting at least a part of the terminal active hydrogen of the addition product with a fluorine-containing group.