This telephone directory assistance system accepts a request for a telephone number of a registrant, and judges whether the registrant is registered in a telephone number data base. When the registrant is registered in the telephone number data base, the telephone directory assistance system judges whether a message from the inquirer is transmitted to the registrant without informing the telephone number to the inquirer based on a telephone number disclosing condition registered in the telephone number data base. Then, in a case of transmission, the inquirer is caused to input a message and the inputted message is informed to the registrant.