The invention discloses an automatic measuring device of coating layer ND direction film thickness, which is used on multiple-face fetching coating equipment. The multiple-face fetching coating equipment is provided with a beam and a plurality of first sensors installed on the beam. The automatic measuring device comprises a slide block, a telescopic mechanical arm, a second sensor and a driving device, wherein the slide block can be arranged on the beam in a sliding mode; one end of the telescopic mechanical arm is fixed on the slide block; the second sensor is installed on the other end of the telescopic mechanical arm and is at least provided with a first gesture used for measuring the ND direction film thickness; and the driving device drives the slide block to slide on the beam so asto drive the second sensor to move along the ND direction. The invention also discloses an automatic measuring method of coating layer ND direction film thickness. The invention can solve the problemthat the present multiple-face fetching coating layer ND direction film thickness can not be automatically measured, thus reducing damage to a glass substrate, reducing equipment production cost, saving technology movement and time, and improving production efficiency.