An electronic device comprising: a body; a display provided on the body; a band coupled to the body, a first portion of the band extending from a first side of the body and a second portion of the band extending from a second side of the body; and a controller; wherein the controller is configured to: detect a tightness of the band when the band is worn on a first part of a user's body, cause the display to display a first user interface of a first operation mode corresponding to the detected tightness, detect a change of the tightness when the band is moved from the first part to a second part of the user's body, change to a second operation mode corresponding to the detected change of the tightness, and cause the display to display a second user interface of the second operation mode, characterized in that the controller is further configured to: cause the display to display at least one application available in the first operation mode when the band is worn on the first part; and cause the display to display at least one application available in the second operation mode when the band is pushed or pulled to the second part, wherein the first part of the user's body is the user's wrist and the second part of the user's body is the user's forearm, wherein a sensor (31, 32), mounted on at least a part of an inner side of the band, senses an area of contact with the user's body, and the controller is configured to determine the tightness of the band based on the area of contact. a body; a display provided on the body; a band coupled to the body, a first portion of the band extending from a first side of the body and a second portion of the band extending from a second side of the body; and a controller; wherein the controller is configured to: detect a tightness of the band when the band is worn on a first part of a user's body, cause the display to display a first user interface of a first operation mode corresponding to the detected tightness, detect a change of the tightness when the band is moved from the first part to a second part of the user's body, change to a second operation mode corresponding to the detected change of the tightness, and cause the display to display a second user interface of the second operation mode, characterized in that the controller is further configured to: cause the display to display at least one application available in the first operation mode when the band is worn on the first part; and cause the display to display at least one application available in the second operation mode when the band is pushed or pulled to the second part, cause the display to display at least one application available in the first operation mode when the band is worn on the first part; and cause the display to display at least one application available in the second operation mode when the band is pushed or pulled to the second part, wherein the first part of the user's body is the user's wrist and the second part of the user's body is the user's forearm, wherein a sensor (31, 32), mounted on at least a part of an inner side of the band, senses an area of contact with the user's body, and the controller is configured to determine the tightness of the band based on the area of contact.