A microetching agent is an acidic aqueous solution containing an organic acid, cupric ions, and halide ions. The molar concentration of halide ion of the microetching agent is 0.005 to 0.1 mol/L. By bringing the microetching agent into contact with a copper surface, the copper surface is roughened. An average etching amount in the depth direction during roughening is preferably 0.4 μm or less. The microetching agent can impart on copper surfaces a roughened shape having excellent adhesiveness to resins and the like, even with a low etching amount.