A wearable device includes: a touch screen; an acceleration sensor configured to generate an acceleration signal; an optical sensor using a light source and configured to generate a touch interrupt signal; and a control unit configured to detect a wearing state of the wearable device, the wearing state of the wearable device including a not-wearing state for the wearable device, a wrist wearing state, and a hand gripping state on the basis of the acceleration signal and the touch interrupt signal, and to execute a function corresponding to the wearing state of the wearable device.