A wearable smart device comprising: a display configured to display various information; a body configured to support the display , the body having a first prescribed curvature; a band configured to be detachably coupled to the body , the band having a second prescribed curvature, the band having a first end portion and a second end portion opposing the first end portion ; a first connector configured to couple the first end portion of the band to the body , the first connector being configured such that the first end portion of the band is separable from the body ; and a second connector configured to couple the second end portion of the band to the body , the second connector being configured such that the second end portion of the band is separable from the body , wherein the first end portion of the band is separable from the body in a first direction and the second end portion of the band is separable from the body in a second direction different from the first direction, characterized in that , in order for the wearable smart device to be placed on or removed from a user's body, only the first end portion of the band is to be separated from the body in the first direction, and in order to replace the band by a different band , the first and second end portions of the band are both to be separated from the body in the first and second directions respectively, wherein the first direction extends in either a length direction of the body or a circumferential direction of the body , and the second direction extends in either a radial direction of the body or a direction perpendicular to a circumferential direction of the body . a display configured to display various information; a body configured to support the display , the body having a first prescribed curvature; a band configured to be detachably coupled to the body , the band having a second prescribed curvature, the band having a first end portion and a second end portion opposing the first end portion ; a first connector configured to couple the first end portion of the band to the body , the first connector being configured such that the first end portion of the band is separable from the body ; and a second connector configured to couple the second end portion of the band to the body , the second connector being configured such that the second end portion of the band is separable from the body , wherein the first end portion of the band is separable from the body in a first direction and the second end portion of the band is separable from the body in a second direction different from the first direction, characterized in that , in order for the wearable smart device to be placed on or removed from a user's body, only the first end portion of the band is to be separated from the body in the first direction, and in order to replace the band by a different band , the first and second end portions of the band are both to be separated from the body in the first and second directions respectively, wherein the first direction extends in either a length direction of the body or a circumferential direction of the body , and the second direction extends in either a radial direction of the body or a direction perpendicular to a circumferential direction of the body . <EOS>