A wearable electronic device is disclosed, including: a housing having a front plate disposed facing in a first direction, a rear plate disposed facing in a second direction opposite to the first direction, at least a part of the rear plate substantially transparent, and a side member defining a space between the front plate and the rear plate, a substrate disposed within the space, a biometric sensor module disposed between the substrate and the rear plate including at least one light source configured to emit light to an exterior of the wearable electronic device and at least one light detector configured to receive reflected light corresponding to the emitted light reflected from the exterior, and at least one magnetic substance disposed between the light source and the light detector to limit an amount of light reaching the biometric sensor module other than the reflected emitted light.