A magnetron sputtering device in one embodiment of the present disclosure includes a support table supporting thereon a base substrate, and a floating mask arranged at a first side of the support table and substantially parallel to the support table. The sputtering gap measurement apparatus includes: a horizontal testing platform arranged on the support table during the measurement, a first edge of the horizontal testing platform being flush with an edge of the first side of the support table in the case that the horizontal testing platform is located at a first position; a first movement mechanism configured to control the horizontal testing platform to move in a direction close to the floating mask, the horizontal testing platform being in contact with the floating mask in the case that the horizontal testing platform has moved to a second position; and a distance measurement mechanism configured to measure a movement distance of the horizontal testing platform from the first position to the second position.