To provide an electronic mail device, an information adding program for an electronic mail and an information adding method for an electronic mail that are capable of saving, when sending the electronic mail, a labor for transmitting the mail by automatically adding information related to a text that is to be transmitted. An input of an electronic mail created by a user is accepted, a keyword is acquired from the electronic mail, additional information corresponding to the keyword is searched for from an additional candidate storage unit stored with candidates for the additional information to the mail, etc. transmitted and received in the past, and the searched additional information is added to the electronic mail.