Whether mail transmitted is unwanted mail is discriminated even in a case where the mail is transmitted from a zombie PC is determined by an unwanted mail discriminating apparatus. The unwanted mail discriminating apparatus has a mail receiver for receiving e-mail; an information extractor for extracting discrimination information for discrimination on whether or not unwanted mail, from the e-mail received; a reliability evaluating part (a sender information reliability evaluator and a URL information reliability evaluator) for connecting to a reliability evaluation database storing information corresponding to the discrimination information, which is for evaluating reliability of the discrimination information, and for evaluating the reliability of the extracted discrimination information with reference to the information stored in the reliability evaluation databases; and a discriminator for discriminating whether the received e-mail is unwanted mail, based on the reliability of the discrimination information evaluated.