Abstract: When a midfoot portion of a sole is divided by a predetermined sole center line into a medial midfoot region and a lateral midfoot region one on each side in the foot width direction, a rigidity lowering portion, which is provided in the medial midfoot region, is provided and, in such a manner that the bending rigidity of the medial midfoot region around a foot width direction axis becomes smaller than that of the lateral midfoot region, the rigidity lowering portion in the medial midfoot region reduces the bending rigidity of the medial midfoot region due to another factor other than the shape of the medial edge and the shape of the lateral edge of the sole in a planar view.

Abstract: A design element index input unit 10 inputs multiple design element indexes obtained by quantifying design in association with multiple portions constituting shoes. A learning unit 40 uses, as teacher data, pairs of multiple design element indexes and an impression index to learn correlations between multiple design element indexes and the impression index, and creates an impression estimation model. By means of a learned impression estimation model, an impression index estimation unit 60 estimates an impression index obtained by quantifying an impression of shoes, based on a set of multiple design element indexes that have been input. An output unit 70 outputs the estimated impression index.