A portable electronic device to be worn around a user's neck comprising: an elastic band located at the user's back neck when being worn; a pair of housings, wherein the housings are coupled respectively to both ends of the elastic band, each housing having an internal space, wherein an overall profile of the portable electronic device forms a C-shaped curved line, each housing comprises: a button hole formed in the housing; and a button unit arranged in the button hole of the housing, the button unit including: a top button coupled to the housing to cover the button hole, the top button forming a rectangular form having a first length in a first direction in width direction of the housing that is longer than a second length in a second direction thereof, the second direction extends in longitudinal direction of the housing, the top button having an exposed top surface and a bottom surface; a button frame provided in the housing, one portion of the button frame being coupled to the bottom surface of the top button, another portion of the button frame being located in the internal space of the housing and coupled to the housing, and a bottom surface of the button frame having an actuator projecting therefrom; and a dome switch pressable by the actuator to generate a signal when the top button is pressed. an elastic band located at the user's back neck when being worn; a pair of housings, wherein the housings are coupled respectively to both ends of the elastic band, each housing having an internal space, wherein an overall profile of the portable electronic device forms a C-shaped curved line, each housing comprises: a button hole formed in the housing; and a button unit arranged in the button hole of the housing, the button unit including: a top button coupled to the housing to cover the button hole, the top button forming a rectangular form having a first length in a first direction in width direction of the housing that is longer than a second length in a second direction thereof, the second direction extends in longitudinal direction of the housing, the top button having an exposed top surface and a bottom surface; a button frame provided in the housing, one portion of the button frame being coupled to the bottom surface of the top button, another portion of the button frame being located in the internal space of the housing and coupled to the housing, and a bottom surface of the button frame having an actuator projecting therefrom; and a dome switch pressable by the actuator to generate a signal when the top button is pressed. a button hole formed in the housing; and a button unit arranged in the button hole of the housing, the button unit including: a top button coupled to the housing to cover the button hole, the top button forming a rectangular form having a first length in a first direction in width direction of the housing that is longer than a second length in a second direction thereof, the second direction extends in longitudinal direction of the housing, the top button having an exposed top surface and a bottom surface; a button frame provided in the housing, one portion of the button frame being coupled to the bottom surface of the top button, another portion of the button frame being located in the internal space of the housing and coupled to the housing, and a bottom surface of the button frame having an actuator projecting therefrom; and a dome switch pressable by the actuator to generate a signal when the top button is pressed. a top button coupled to the housing to cover the button hole, the top button forming a rectangular form having a first length in a first direction in width direction of the housing that is longer than a second length in a second direction thereof, the second direction extends in longitudinal direction of the housing, the top button having an exposed top surface and a bottom surface; a button frame provided in the housing, one portion of the button frame being coupled to the bottom surface of the top button, another portion of the button frame being located in the internal space of the housing and coupled to the housing, and a bottom surface of the button frame having an actuator projecting therefrom; and a dome switch pressable by the actuator to generate a signal when the top button is pressed.