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PROBLEM TO BE SOLVED : To provide a ferritic stainless steel suitable for a system for accumulating heat using molten nitrate to use the heat at 400 to 600°C as energy, and a heat collection tube and a heat accumulation system using the molten nitrate as a heat accumulation medium.SOLUTION : A ferrite stainless steel excellent in molten nitrate corrosion resistance includes, by mass%, ≤0.03% C, ≤1.5% Si, ≤2.0% Mn, ≤0.08% P, ≤0.01% S, ≤1.0% Ni, ≥10% and ≤35% Cr, ≤2.5% Mo, ≥0.10% and ≤0.80% Nb, ≤0.5% V, ≤0.03% N, and if required, further includes a predetermined amount of one or more of Cu, Ti, Zr, W, Co, Al, and rare earth elements, with the balance of Fe and inevitable impurities. In the ferrite stainless steel, the ratio of elements constituting the oxide, other than oxygen, formed in a part which comes into contact with molten nitrate at ≤600°C satisfies Si+Mo≤20% and Mn+Nb≥20% in terms of atom%.