To obtain a microbicide composition which comprises a hydantoin halide compound aqueous slurry capable of being stably stored for a long period.

This microbicide composition is characterized by comprising an aqueous slurry containing (A) the hydantoin halide compound represented by formula (1), (B) a benzimidazole compound represented by formula (2), and (C) a monoethylenic unsaturated carboxylic acid polymer having substituents selected from sulfonic groups and/or phosphonic groups and/or its salt. The microbicide composition is suitably characterized by comprising (A) 100 pts. wt. of the hydantoin halide compound, (B) 1 to 15 pts. wt. of the benzimidazole compound, and (C) 1 to 15 pts. wt. of the monoethylenic unsaturated carboxylic acid polymer having the substituents selected from the sulfonic groups and/or the phosphonic groups.