Anguilliformes breeding water contains a thyroid hormone such as thyroxine, and a method for rearing anguilliformes includes a step for administering a thyroid hormone such as thyroxine, wherein the amount of the thyroid hormone to be administered changes as the anguilliforme fingerling changes from a transformation start phase (stage 1) to a transformation final phase (stage 2), and the amount of the thyroid hormone to be administered in the transformation final phase (stage 2) is less than the amount of the thyroid hormone to be administered in the transformation start phase (stage 1).
