In a voice search device, a processor acquires a search word, converts the search word into a phoneme sequence, acquires, for each frame, an output probability of a feature quantity of a target voice signal being output from each phoneme included in the phoneme sequence, and executes relative calculation of the output probability acquired from each phoneme, based on an output probability acquired from another phoneme included in the phoneme sequence. In addition, the processor successively designates likelihood acquisition zones, acquires a likelihood indicating how likely a designated likelihood acquisition zone is a zone in which voice corresponding to the search word is spoken, and identifies from the target voice signal an estimated zone for which the voice corresponding to the search word is estimated to be spoken, based on the acquired likelihood.