1. A speech synthesis dictionary generation apparatus for generating a speech synthesis dictionary containing a model of an object speaker based on speech data of the object speaker, the apparatus comprising: a speech analyzer configured to analyze the speech data and generate a speech database containing data representing characteristics of utterance by the object speaker; a speaker adapter configured to generate the model of the object speaker by performing speaker adaptation of converting a predetermined base model to be closer to characteristics of the object speaker based on the speech database; a target speaker level designation unit configured to accept designation of a target speaker level that is a speaker level to be targeted, the speaker level representing at least one of a speaker's utterance skill and a speaker's native level in a language of the speech synthesis dictionary; and a determination unit configured to determine a value of a parameter related to fidelity of reproduction of speaker properties in the speaker adaptation, in accordance with a relationship between the designated target speaker level and an object speaker level that is the speaker level of the object speaker, wherein the determination unit is configured to determine the value of the parameter so that the fidelity is lower when the designated target speaker level is higher than the object speaker level, compared to when the designated target speaker level is not higher than the object speaker level, and the speaker adapter is configured to perform the speaker adaptation in accordance with the value of a parameter determined by the determination unit.