An automatic angle-measured apparatus has: a clamping plate; a driving seat; a driving unit coupled to the clamping plate and the driving seat; an encoding unit installed an end of the driving unit, the end facing the driving seat, the encoding unit signal connected to the driving unit; at least one attitude sensor installed in the driving seat; and a controlling unit signal connected to the attitude sensor and the encoding unit; wherein, the attitude sensor senses not rotated the driving seat to generate a first signal; the attitude sensor senses the driving seat after rotating to a predetermined degree, the attitude sensor generates a second signal; the controlling unit calculates a offset value by the first signal and the second signal, the controlling unit controls the driving unit to rotate to a predetermined degree, the encoding unit generates a location information by the predetermined degree of the driving unit; the controlling unit calculates an angle information and a compensation by the first signal, the second signal and the location information, the controlling unit processes a correction procedure by the compensation.