A casing assembly for electronic device , comprising: a first casing ; a second casing ; and a hinge assembly , comprising: a fixed frame , fixed to the first casing ; a shaft , rotatably disposed on the fixed frame ; a rotatable frame , fixed to the shaft and the second casing , wherein the rotatable frame has a first positioning structure , the rotatable frame comprises a base and two rotatable components , the base is fixed to the shaft , the two rotatable components are rotatably disposed on the base and fixed to the second casing , and a rotation axis (A1) of the two rotatable components relative to the base is perpendicular to a rotation axis (A2) of the base relative to the fixed frame via the shaft ; and a cover , fixed to the first casing ; wherein the fixed frame or the cover has at least one second positioning structure , and the first positioning structure and the at least one second positioning structure are cooperated with each other so as to limit a rotatable range of the base of the rotatable frame relative to the fixed frame via the shaft ; characterized in that the cover comprises a horizontal plate and a vertical plate , the vertical plate stands on the horizontal plate , the horizontal plate has a sleeve hole, an opening of the sleeve hole is located at one side of the horizontal plate located opposite to the vertical plate , the horizontal plate is located between the rotatable frame and the fixed frame and is sleeved on the shaft through the sleeve hole. a first casing ; a second casing ; and a hinge assembly , comprising: a fixed frame , fixed to the first casing ; a shaft , rotatably disposed on the fixed frame ; a rotatable frame , fixed to the shaft and the second casing , wherein the rotatable frame has a first positioning structure , the rotatable frame comprises a base and two rotatable components , the base is fixed to the shaft , the two rotatable components are rotatably disposed on the base and fixed to the second casing , and a rotation axis (A1) of the two rotatable components relative to the base is perpendicular to a rotation axis (A2) of the base relative to the fixed frame via the shaft ; and a cover , fixed to the first casing ; wherein the fixed frame or the cover has at least one second positioning structure , and the first positioning structure and the at least one second positioning structure are cooperated with each other so as to limit a rotatable range of the base of the rotatable frame relative to the fixed frame via the shaft ; a fixed frame , fixed to the first casing ; a shaft , rotatably disposed on the fixed frame ; a rotatable frame , fixed to the shaft and the second casing , wherein the rotatable frame has a first positioning structure , the rotatable frame comprises a base and two rotatable components , the base is fixed to the shaft , the two rotatable components are rotatably disposed on the base and fixed to the second casing , and a rotation axis (A1) of the two rotatable components relative to the base is perpendicular to a rotation axis (A2) of the base relative to the fixed frame via the shaft ; and a cover , fixed to the first casing ; wherein the fixed frame or the cover has at least one second positioning structure , and the first positioning structure and the at least one second positioning structure are cooperated with each other so as to limit a rotatable range of the base of the rotatable frame relative to the fixed frame via the shaft ; characterized in that the cover comprises a horizontal plate and a vertical plate , the vertical plate stands on the horizontal plate , the horizontal plate has a sleeve hole, an opening of the sleeve hole is located at one side of the horizontal plate located opposite to the vertical plate , the horizontal plate is located between the rotatable frame and the fixed frame and is sleeved on the shaft through the sleeve hole. <EOS>