A data converting apparatus and a data converting program are suitable to quantitatively estimate, based on a temporal alteration of a stimulus value, a temporal alteration of a sensitivity brought to human beings. The data converting apparatus includes a decomposing unit subjecting temporal alteration data of a stimulus value to wavelet decomposition to extract plural time-frequency components contained in the temporal alteration data, a weighting unit weighting the plural extracted time-frequency components weighting coefficients which are predetermined based on a relationship between a temporal alteration of a stimulus value and a temporal alteration of a sensitivity of human beings to the stimulus value, and a synthesizing unit subjecting the plural weighted time-frequency components to wavelet synthesis to estimate a sensitivity brought to human beings when the stimulus value is subjected to temporal alteration according to the temporal alteration data.