An electronic device (200, 600) comprising: a housing; an optical element unit (310, 671) configured to emit light toward a user's body, receive light reflected from the user's body, and convert the received light into a first signal; an IC element (390, 679) configured to convert the first signal provided from the optical element unit into a second signal, and provide the second signal to a main circuit board disposed in the housing; a first circuit board (350, 675) disposed between the optical element unit and the IC element and electrically connected to the optical element unit and the IC element; a second circuit board (370, 677) including at least one first opening in which the IC element is mounted; and a display device, wherein the housing includes at least one transparent region such that the light generated by the optical element unit is transmitted through the transparent region to an exterior of the housing, wherein the optical element unit includes at least one light source configured to emit the light toward the user's body and a photodiode configured to receive the light reflected from the user's body and convert the received light into the first signal, and wherein the electronic device further comprises a cover unit including at least one second opening in which the at least one light source is mounted, such that the at least one light source is exposed toward the user's body, and at least one third opening in which the photodiode is mounted, such that the photodiode is exposed toward the user's body, wherein the main circuit board is disposed between the display device and the first circuit board and includes a groove disposed to correspond to the at least one first opening, and wherein a thickness of the IC element is greater than a thickness of the second circuit board, such that a first portion of the IC element is accommodated in the at least one first opening and a remaining portion of the IC element is accommodated in the groove. a housing; an optical element unit (310, 671) configured to emit light toward a user's body, receive light reflected from the user's body, and convert the received light into a first signal; an IC element (390, 679) configured to convert the first signal provided from the optical element unit into a second signal, and provide the second signal to a main circuit board disposed in the housing; a first circuit board (350, 675) disposed between the optical element unit and the IC element and electrically connected to the optical element unit and the IC element; a second circuit board (370, 677) including at least one first opening in which the IC element is mounted; and a display device, wherein the housing includes at least one transparent region such that the light generated by the optical element unit is transmitted through the transparent region to an exterior of the housing, wherein the optical element unit includes at least one light source configured to emit the light toward the user's body and a photodiode configured to receive the light reflected from the user's body and convert the received light into the first signal, and wherein the electronic device further comprises a cover unit including at least one second opening in which the at least one light source is mounted, such that the at least one light source is exposed toward the user's body, and at least one third opening in which the photodiode is mounted, such that the photodiode is exposed toward the user's body, wherein the main circuit board is disposed between the display device and the first circuit board and includes a groove disposed to correspond to the at least one first opening, and wherein a thickness of the IC element is greater than a thickness of the second circuit board, such that a first portion of the IC element is accommodated in the at least one first opening and a remaining portion of the IC element is accommodated in the groove. wherein the main circuit board is disposed between the display device and the first circuit board and includes a groove disposed to correspond to the at least one first opening, and wherein a thickness of the IC element is greater than a thickness of the second circuit board, such that a first portion of the IC element is accommodated in the at least one first opening and a remaining portion of the IC element is accommodated in the groove.