A drug and a composition for inhibiting biofilm formation are provided. A biofilm formation inhibitor composition containing the following component (A): (A) at least one or more selected from compounds represented by Formula (1) to Formula (4): wherein R1 to R5 each represent an alkyl group or the like EO represents an ethyleneoxy group p represents an integer from 0 to 5 and m+n represents a number from 0 to 30, or a salt thereof and (B) a surfactant.
