PROBLEM TO BE SOLVED: To provide a bactericide composition having excellent bactericidal effect on bacterial spores on which conventional antiseptics has no effect, less in limitation of sterilization targets and excellent in safety and handleability.SOLUTION: There is provided a bactericide composition containing one or more kinds selected from a group consisting of a polyalkylene biguanide compound represented by the formula (1) and a salt thereof and an alkali group and having pH of the composition of 12.5. A composition containing further quaternary ammonium salt and/or alcohol has enhanced bactericidal effect and exhibits bactericidal effect by short time action. In the formula (1), Rand n are same as described in the application.SELECTED DRAWING: None