1. A speech recognition method, comprising the following steps: a reference step of referring to, in a computation of a likelihood of an acoustic model referred to upon computing an accumulated likelihood of a hypothesis, at least one subword model determined depending on its context subwords with respect to each hypothesis; and a first likelihood-computation step of computing, based on a speech to be recognized and each of the subword models, likelihoods of acoustic models of the respective subword models, and setting a maximum value of the computed likelihoods as a likelihood of an acoustic model corresponding to the hypothesis.