A film formation method for a metallic coating, wherein a metallic coating derived from metal ions is formed on a surface of a substrate by disposing a solid electrolyte membrane between an anode and the substrate that serves as a cathode, pressing the substrate by the solid electrolyte membrane with a fluid pressure of an electrolyte that is disposed between the anode and the solid electrolyte membrane and contains the metal ions, and applying a voltage between the anode and the substrate in a state of pressing the substrate, the method comprises: measuring an alternating current impedance between the anode and the substrate in a state where the solid electrolyte membrane is in contact with the substrate; determining whether an imaginary component at a predetermined frequency of the alternating current impedance is equal to or more than a preliminarily set film-formable value or not, the imaginary component at the predetermined frequency indicating a contact state between the solid electrolyte membrane and the substrate, and a film formation becoming performable when the imaginary component is equal to or more than the film-formable value; when the imaginary component is determined to be smaller than the film-formable value in the determining step, releasing the pressing of the substrate by the solid electrolyte membrane to separate the solid electrolyte membrane from the substrate, then re-tensioning the solid electrolyte membrane with a constant tensile force, then remeasuring the alternating current impedance in the state where the solid electrolyte membrane is in contact with the substrate, then redetermining whether the imaginary component at the predetermined frequency is equal to or more than the film-formable value or not, wherein when the imaginary component is determined to be smaller than the film-formable value in the redetermining step, the releasing, re-tensioning, remeasuring and redetermining steps are repeated until the imaginary component is determined to be equal to or more than the film-formable value; and when the imaginary component is determined to be equal to or more than the film-formable value, forming the metallic coating in a state where the substrate is pressed by the solid electrolyte membrane. measuring an alternating current impedance between the anode and the substrate in a state where the solid electrolyte membrane is in contact with the substrate; determining whether an imaginary component at a predetermined frequency of the alternating current impedance is equal to or more than a preliminarily set film-formable value or not, the imaginary component at the predetermined frequency indicating a contact state between the solid electrolyte membrane and the substrate, and a film formation becoming performable when the imaginary component is equal to or more than the film-formable value; when the imaginary component is determined to be smaller than the film-formable value in the determining step, releasing the pressing of the substrate by the solid electrolyte membrane to separate the solid electrolyte membrane from the substrate, then re-tensioning the solid electrolyte membrane with a constant tensile force, then remeasuring the alternating current impedance in the state where the solid electrolyte membrane is in contact with the substrate, then redetermining whether the imaginary component at the predetermined frequency is equal to or more than the film-formable value or not, wherein when the imaginary component is determined to be smaller than the film-formable value in the redetermining step, the releasing, re-tensioning, remeasuring and redetermining steps are repeated until the imaginary component is determined to be equal to or more than the film-formable value; and when the imaginary component is determined to be equal to or more than the film-formable value, forming the metallic coating in a state where the substrate is pressed by the solid electrolyte membrane.