A communication apparatus is provided for transmitting and receiving a plurality types of data with a TDM slot, changing the type of the data by switching a mode. The communication apparatus includes mode switching unit 101 and data dividing unit 102. The mode switching unit 101 judges whether a length of the second data is less than a predetermined value when it detects a necessity for transmitting the second data during a transmission of the first data. If less, mode switching unit 101 inserts a non-acknowledgement-type mode switch directive in the time slot data and transmits the time slot data by an interrupt. The data dividing unit 102 identifies the second data included in the received time slot data if it is judged that the received time slot data includes the non-acknowledgement-type mode switch directive, and processes the data according to the identification.