1. A speech synthesis apparatus comprising: a text analysis unit configured to analyze an input text and output language information; a dictionary storage unit configured to store a first prosodic control dictionary of a target speaker and a second prosodic control dictionary of one standard speaker or each of a plurality of standard speakers; a prosodic parameter generation unit configured to generate a first prosodic parameter using the first prosodic control dictionary and generate one or a plurality of second prosodic parameters using the second prosodic control dictionary, based on the language information; a normalization unit configured to normalize the one or the plurality of second prosodic parameters based a normalization parameter; a prosodic parameter interpolation unit configured to interpolate the first prosodic parameter and the one or the plurality of normalized second prosodic parameters based on weight information to generate a third prosodic parameter; and a speech synthesis unit configured to generate synthesized speech in accordance with the third prosodic parameter.