Provided is a disinfectant containing an [alpha],[beta]-unsaturated aldehyde represented by general formula (1) as an active ingredient (wherein: R1-R3 each independently represent a hydrogen atom, an alkyl group having 1-10 carbon atoms, an alkenyl group having 2-10 carbon atoms, or an aryl group having 6-12 carbon atoms； R1 may be bonded with R2 or R3 to form an alkylene group having 2-6 carbon atoms； and R1 and R2 would not simultaneously be hydrogen atoms).一種殺菌劑，其係以下述通式(1)所示之α,β-不飽和醛作為有效成分，(R1~R3各自係獨立而表示氫原子、碳數1~10之烷基、碳數2~10之烯基或碳數6~12之芳基；但是，R1可與R2或R3互相連結而構成碳數2~6之伸烷基，且R1及R2不同時為氫原子)。
