A levelling spacer device for the laying of sheet-shaped products for coating surfaces, including a base positionable posteriorly to a laying surface of at least two sheet-shaped products arranged adjacent and side by side relative to a side-by-side direction, a separator element which rises perpendicularly from the base and is configured to slip between facing lateral sides of the two sheet-shaped products placed side by side, a pusher element adapted to cooperate with the separator element, and a plate provided with at least one through opening configured to be inserted onto the separator element, wherein the plate is configured to be interposed between the pusher element and the base and includes a first flat surface facing the base wherefrom at least one lamella is projecting which is configured to slip between a lateral side of a sheet-shaped product and the separator element.