The present invention provides an epigallocatechin gallate derivative (EGCG derivative) that has excellent safety and antibacterial properties. An epigallocatechin gallate derivative represented by the following chemical formula (1), an isomer thereof, or a salt thereof is used as an antibacterial agent. In the formula, R1 to R6 are each a hydrogen atom, halogen, sodium, potassium, or a straight-chain or branched, saturated or unsaturated acyl group and may be identical to or different from one another. The acyl group may be substituted further with one or more substituents. At least one of the R1 to R6 is the acyl group. R7 to R16 are each a hydrogen atom, halogen, sodium, or potassium and may be identical to or different from one another.
