A coefficient-data generating apparatus generates coefficient data of an estimating equation used to convert a first information signal including pieces of information data into a second information signal including pieces of information data. The coefficient-data generating apparatus includes a determining unit determining whether a subject point in a second learning signal corresponding to the second information signal is a feature point having a predetermined feature; a data selector selecting pieces of information data at adjacent points of the subject point in the second learning signal, based on a first learning signal corresponding to the first information signal; and a calculator calculating the coefficient data using information data at the subject point in the second learning signal, the subject point being determined as the feature point by the determining unit, and the pieces of information data selected in association with the subject point by the data selector.