To provide a multiplexer by which information is multiplexed and transmitted efficiency with a simple configuration and where malfunction of a receiver side receiving multiplexed information can surely be prevented.

A multiplexer means 130 multiplexes coded data from coding means 110, 120 with relation information (PSI information) from a control means 140. In the case of switching a coding mode by a changeover means 150, the control means 140 interrupts multiplexing of coded data by the multiplexer means 130 until update of the relation information is finished (end of generation of new relation information).