To provide a technology for accurately estimating the time history data of unknown condition from stored time history data.

This data estimating apparatus includes storing means for storing time history data of a plurality of known conditions, converting means for acquiring amplitude data and phase data of each known condition by converting the time history data into a frequency region, amplitude estimating means for estimating the amplitude data of the unknown condition based on the amplitude data of the plurality of known conditions, phase estimating means for estimating the phase data of the unknown condition based on the phase data of the plurality of known conditions, and inverse converting means for creating time history data of the unknown conditions by inversely converting the amplitude data and phase data of the unknown conditions into a time region.