A portable telephone radio unit is disclosed which allows a user to recognize an incomplete state of data communication which occurs with a terminal equipment because of deterioration of the communication state by radio wave interference upon channel changing over in the course of a standby channel selection operation or during communication. A signal processing section performs information analysis of a signal selected by a control circuit section from among reception signals of an antenna whose levels are measured by a radio circuit section upon channel changing over in the course of a standby channel selection operation or during communication. The control circuit section detects loss of frame synchronization, deterioration in bit error rate, unfavorable reception of broadcast information or interruption of radio waves which is a condition of radio wave interference. Then, if a waiting condition is not satisfied, then the control circuit section controls a warning display section to display a warning of radio wave interference. The radio wave interference warning is erased when the cause of the radio wave interference disappears.