Iron core for transformer

An iron core for a transformer, comprising

• a plurality of grain-oriented electrical steel sheets stacked together,
• wherein at least one of the plurality of grain-oriented electrical steel sheets:
• (1) has a closure domain formation region extending from one end of the grain-oriented electrical steel sheet to the other end in a rolling direction in which a plurality of closure domains extending in a direction crossing the rolling direction are present at an interval in the rolling direction, and
• a closure domain non-formation region in which no closure domains are formed;
• and
• (2) has an area ratio R of 0.10% to 30%, the area ratio R being an area ratio, to the whole grain-oriented electrical steel sheet, of the closure domain formation region, where a shrinkage amount of the grain-oriented electrical steel sheet at a maximum displacement point when excited in the rolling direction at a maximum magnetic flux density of 1.7 T and a frequency of 50 Hz is at least 2×10−7 less than a shrinkage amount of the grain-oriented electrical steel sheet in the closure domain non-formation region,
• the maximum displacement point being defined as a point where an amount of expansion or shrinkage of the grain-oriented electrical steel sheet is maximum when excited under the maximum magnetic flux density and the frequency.