To provide a response system and a response content control method, capable of outputting a proper response sentence.

This response system concerned in one embodiment is a response system for outputting the response sentence with respect to an input input-sentence, and has a microphone 31 for inputting the input sentence, a language understanding part 12 for understanding language information of the input sentence input into the microphone, a dialogue management part 13 for determining a response proposal sentence in response to the language information, a response sentence generating part 14 for generating the response sentence based on the response proposal sentence, a speaker 32 for outputting the response sentence generated by the response sentence generating part 14. The dialogue management part 13 calculates similarity between the response proposal sentence and a prohibited sentence, referring to a prohibited sentence database 16 storing the prohibited sentence. The dialogue management part 13 limits an output of the response proposal sentence in response to a comparison result of the similarity with a determination value.