This invention relates to a metal catalyst, a manufacturing method of the metal catalyst, and an electrochemical reduction method.The metal catalyst is manufactured by a method comprising providing a conductor to one side of an insulator, providing a fluid including a metal ion and an electron mediator to the other side of the insulator and providing a voltage to the conductor.The electrochemical reduction method comprises providing a conductor to one side of an insulator, providing a fluid including reduction material and an electron mediator to the other side of the insulator and providing a voltage to the conductor.