A device for controlling connection of a built-in type ear-microphone for a portable radio terminal includes a vocoder, which has the speaker and microphone amplifier of the portable radio terminal and an ear-microphone amplifier; a first logic combination means for logically combining a signal output from the speaker amplifier and a signal output from the ear-microphone amplifier so as to prevent generation of noises due to short-circuit of a microphone signal and a speaker signal while an earphone plug is inserted in an earphone jack; a comparator for comparing an electric signal sensed at the earphone jack with a reference voltage; a second logic combination means for logically combining an output of the first logic combination means and an output of the comparator to generate a jack detection signal; and a central processing unit for generating a control signal for enabling the vocoder to switch an audio signal path to the ear-microphone amplifier, upon detection of the jack detection signal during a call.