To provide a highly conductive Cu alloy which is advantageous in that an alloying element added to Cu is first reacted with oxygen contained in a gas atmosphere or solid in contact with the Cu member to form an oxide film which can prevent oxidation of Cu. The copper alloy comprises copper (Cu) containing an inevitable impurity, and an element added to the copper, wherein the added element is capable of being dissolved in the copper in an amount of 0.1 to 20 at. %, wherein the added element has an oxide formation free energy smaller than that of Cu and has a diffusion coefficient in Cu larger than the self-diffusion coefficient of Cu.