A design supporting device includes a calculator that calculates an estimated value of a width, shifted by etching, of a wiring arranged in each of partial regions formed by dividing a layout region of a circuit to be designed on basis of a density of the wiring of the partial region, a length of a circumference of the wiring and a distance between the partial region and another partial region affecting the partial region, and uses the calculated estimated value to recalculate the density of the wiring of the partial regions, and a changer that changes the density of the wiring on basis of relationships between a recalculated density of the wiring and a preset threshold for the density.