The present invention relates to a method of displaying several types of messages all together through a single window and of enabling a user to write and transmit a message with no consideration of message type. This unified message management method displays various types of messages all together along with their respective message types through a single window, converts the type of a written message, if needed, to match it to a protocol determined based on information written in its field distinguishing a message type, and transmits the type-converted message, whereby a user can confirm all types of received messages at a time and user's inconvenience that a message type to write should be distinguished in advance prior to choosing a message input screen can be removed.