1. A machine translation apparatus, comprising: at least a processor and memory; a speech recognition unit configured to perform speech recognition of speech in source language to obtain a recognition result text as a result of the speech recognition; an analysis unit configured to divide the recognition result text into a plurality of parts to obtain a plurality of source language strings for translating from the source language into target language; a translation unit configured to translate the plurality of source language strings into a plurality of target language strings in a chronological order; a detection unit configured to detect ambiguity in interpretation of the speech corresponding to a first target language string of the target language strings, based on a relationship between the first target language string and one or more second target language strings, the second target language strings chronologically preceding the first target language string; and an addition unit configured to add an additional phrase to the first target language string if ambiguity is detected, the additional phrase being one of words and phrases to interpret uniquely a modification relationship between the first target language string and the second target language strings, wherein the detection unit analyzes the modification relationship of words and phrases between the first target language string and the second target language strings, and detects the ambiguity if at least one of the first target language string and the second target language strings has two or more modification relationships.