Provided an antimicrobial substance that includes a base material layer, and a copper-tin alloy layer 5-200 nm in thickness disposed on the base material layer, the copper-tin alloy layer containing copper in an amount of more than 60 atomic percent but not more than 90 atomic percent, and containing tin in an amount of not less than 10 atomic percent but less than 40 atomic percent. The copper-tin alloy layer includes a Cu41Sn11 crystalline phase, and a Cu3Sn crystalline phase. The Q value (Ω/(nm·Cu atomic percent)), which is derived by dividing the sheet resistance (Ω) of the copper-tin alloy layer by the thickness of the copper-tin alloy layer and the copper content (Cu atomic percent), is 1.5×10−4-6.0×10−4.
