To provide a strength estimation apparatus for estimating information on a probability density distribution of the maximum stress and a frequency distribution of a stress amplitude if the stress under a random load is represented as a frequency spectrum such as a power spectrum and a time history waveform.

The strength estimation apparatus for estimating a strength of a structure includes: a frequency spectrum data inputting means for inputting frequency spectrum data of a random vibration waveform of the stress generated in the structure; a stress information estimating means for estimating stress information including a statistical property from a plurality of the random vibration waveforms obtained by generating a plurality of waveforms having a frequency characteristic equivalent to the frequency spectrum; a material strength data inputting means for inputting material strength data of the structure; and a damage determining means for determining a damage of the structure from the stress information and the material strength data.