A levelling spacer device for laying slab-shaped products including a base having a lower surface and an opposite upper surface defining a support plane for at least two tiles placed side by side, which is placed at a first distance from the lower surface, a spacer bridge provided with two legs placed side by side between each other along a flanking direction and each one rising from a portion of the opposite upper surface. Each leg is frangibly connected to the respective base portion by a predefined fracture line placed at a second distance from the lower surface greater than the first distance. A crosspiece, joins the top of the two legs, and a through opening peripherally delimited at the top by the crosspiece, laterally by the legs and at the bottom by a central portion of the upper surface coplanar with the support plane.