PURPOSE: To provide a method and device for sent and received message monitoring which can read the names of sent and received messages and their message data together.

CONSTITUTION: The method and device have a message registration area 5 wherein the kind of transmission and reception of the sent and received messages, their message discrimination numbers, and message data are registered as order codes, a data storage area 6 in which the message data are stored corresponding to the order codes. a terminal device 1, an on-line control part 2, a comparing circuit 4, and a buffer memory area 3 in which a message discrimination area 7 wherein the order code matching with an inputted message discrimination number is read out of the message registration area 5 by the comparator 4 and written and a message data storage area 8 wherein the message data corresponding to the order code are read out of the data storage area 6 and written are designated.