PURPOSE: To obtain the subject composition, containing β-bromo-β-nitrostyrene and a specific isothiazolone-based compound as active ingredients, having a wide antimicrobial spectrum, hardly emerging resistant germs even in use thereof for a long period and capable of sufficiently exhibiting effects thereof even at a low concentration.

CONSTITUTION: The subject composition is produced by blending (A) β-bromoβ- nitrostyrene with (B) at least one selected from 1,2benzisothiazolin-3-one expressed by formula I (R2 is H or substituent group) and compounds expressed by formula II (R1 is 4-12C alkyl; X1 and X2 are H or halogen) at (50:1) to (1:50) ratio as active ingredients. For example, solutions in which the active ingredients are dissolved in a solvent, flowable agents prepared by dispersion thereof as particles in water or solid agents obtained by kneading the active ingredients in synthetic resins, etc., are cited as the form of formulations. The aforementioned composition is employed for control of slimes in paper and pulp mills, antimicrobial and antifungal treatment of starches, pigments, adhesives, etc., wood, fiber, etc.