A metal substrate for a catalytic converter, comprising: a honeycomb core containing a flat metal foil and a corrugated metal foil laminated onto each other; and a metal outer jacket surrounding an outer circumferential surface of the honeycomb core, wherein: the flat metal foil and the corrugated metal foil disposed in an gas inlet side joining section are joined to each other; the flat metal foil and the corrugated metal foil disposed in an outer circumferential joining section are joined to each other, the outer circumferential joining section is connected to an axial end section of the gas inlet side joining section; the gas inlet side joining section extends 5 mm or more and 50% or less of an entire length in an axial direction from a gas inlet side end section of the honeycomb core, across all layers in a radial direction of the honeycomb core; the outer circumferential joining section extends from the axial end section of the gas inlet side joining section toward a gas outlet side end section of the honeycomb core across two or more layers and 1/3 or less of the total number of layers in the radial direction from an outermost circumference of the honeycomb core; the outer jacket and the honeycomb core are joined by interposing a joining layer in a gas outlet side end section area formed between the outer jacket and the honeycomb core and extending from the gas outlet side end section of the honeycomb core in the axial direction; when the joining layer has a length P in the axial direction, P is 2 mm or more and 50 mm or less; the metal substrate being characterized in that: the corrugated metal foil has an impact mitigating section having different wave phases between a front and rear in the axial direction; and the impact mitigating section is formed in a region corresponding to at least the gas inlet side joining section and the outer circumferential joining section; and the impact mitigating section is configured such that an offset width being an axial length of a wave having the same phase is 0.5 mm or more and 50 mm or less and an amount of phase shift between axially neighboring waves is 0.05 mm or more and 5 mm or less. the flat metal foil and the corrugated metal foil disposed in an gas inlet side joining section are joined to each other; the flat metal foil and the corrugated metal foil disposed in an outer circumferential joining section are joined to each other, the outer circumferential joining section is connected to an axial end section of the gas inlet side joining section; the gas inlet side joining section extends 5 mm or more and 50% or less of an entire length in an axial direction from a gas inlet side end section of the honeycomb core, across all layers in a radial direction of the honeycomb core; the outer circumferential joining section extends from the axial end section of the gas inlet side joining section toward a gas outlet side end section of the honeycomb core across two or more layers and 1/3 or less of the total number of layers in the radial direction from an outermost circumference of the honeycomb core; the outer jacket and the honeycomb core are joined by interposing a joining layer in a gas outlet side end section area formed between the outer jacket and the honeycomb core and extending from the gas outlet side end section of the honeycomb core in the axial direction; when the joining layer has a length P in the axial direction, P is 2 mm or more and 50 mm or less; the metal substrate being characterized in that: the corrugated metal foil has an impact mitigating section having different wave phases between a front and rear in the axial direction; and the impact mitigating section is formed in a region corresponding to at least the gas inlet side joining section and the outer circumferential joining section; and the impact mitigating section is configured such that an offset width being an axial length of a wave having the same phase is 0.5 mm or more and 50 mm or less and an amount of phase shift between axially neighboring waves is 0.05 mm or more and 5 mm or less. the corrugated metal foil has an impact mitigating section having different wave phases between a front and rear in the axial direction; and the impact mitigating section is formed in a region corresponding to at least the gas inlet side joining section and the outer circumferential joining section; and the impact mitigating section is configured such that an offset width being an axial length of a wave having the same phase is 0.5 mm or more and 50 mm or less and an amount of phase shift between axially neighboring waves is 0.05 mm or more and 5 mm or less.