According to an embodiment of the present disclosure, there is provided a human body wearable device including: a light emitting unit for generating light to outside, a light receiving unit for receiving light incident from outside; and a control unit for controlling an operation of the light emitting unit and detecting an intensity of light incident on the light receiving unit depending on the operation of the light emitting unit, and detecting a wearing state of the human body wearable device based on an intensity of detected light, wherein the control unit detects the wearing state using a difference value between an intensity of the light incident on the light receiving unit in an ON section of the light emitting unit and that of the light incident on the light receiving unit in an OFF section of the light emitting unit.