PURPOSE: To perform transmission with a certain fixed information volume without drop-out of the latest security information.

CONSTITUTION: A storage device 20 is provided with a first security information storage part 21 where security information which is being transmitted/already transmitted is stored, a second security information storage part 22 where present security information is stored, and a changed information storage part 23 where changed information indicating that present security information has been changed is stored. A controller 40 compares security information stored in the first security information storage part 21 with that in the second security information storage part 22 and has a function to store the changed information in the changed information storage part 23 in the case of noncoincidence between them, and when changed information is stored in the changed information storage part 23 or new security information is inputted, present security information stored in the second security information storage part 22 and changed information stored in the changed information storage part 23 are transmitted from a transmission equipment.