The present invention relates to a metal substrate for a fixing belt, having excellent durability. The metal substrate for a fixing belt of the present invention including an austenite stainless steel including a martensite phase includes: a region of austenite stainless steel including a martensite phase, with a nickel content of 8 mass % or more, sandwiched between regions of austenite stainless steel including a martensite phase, with a nickel content less than 8 mass %, in the thickness direction.