Calibration device and calibration method for calibration of a laser beam horizontal trueness testing device whereby the calibration device comprises an elongated support body for support of an elongated laser housing with a longitudinal axis and a laser source, whereby a laser beam is emittable in a direction of the longitudinal axis. According to the calibration method, calibration parameters are determined based on at least three impinging positions of the laser beam of the laser housing for at least two different rotational positions of the laser housing in a first face and at least one position of the laser housing in a second opposing face.