Disclosed is a device for connecting an ear-microphone to a mobile phone through an interface connector of the mobile phone. The phone includes a codec which has hands-free-kit audio transmission and reception terminals connected to the interface connector. A controller includes first and second interrupt terminals which are used for detecting whether the ear-microphone plug is connected, and whether a call connection/termination key of the ear-microphone is activated, respectively. A first voltage drop detector detects a first voltage drop at the corresponding connection path when the ear-microphone plug is connected through the interface connector, and outputs a first interrupt signal to the first interrupt terminal. A second voltage drop detector detects a second voltage drop at the corresponding connection path when the call connection/termination key is activated with the ear-microphone plug being connected, and outputs a second interrupt signal to the second interrupt terminal.