Apparatus for continuously forming a continuous element made of expanded plastic material comprising: a) a loading section of a loose mass of granules made of expandable plastic material; b) a sintering section of said continuous element made of expanded plastic material, extending downstream of said loading section; c) a stabilizing section of said continuous element made of expanded plastic material, extending downstream of said sintering section; d) a forming tunnel extending along said sintering and stabilizing sections and defined between a pair of lateral walls (19, 20) and a pair of gas permeable conveyor belts (21, 22), respectively lower and upper, said belts (21, 22) being supported by respective lower and upper supporting tracks (23, 24); wherein at least one of the supporting tracks (23, 24) of the gas permeable conveyor belts (21, 22) comprises at least one portion extending in the sintering section, characterized by, that at least one of the supporting tracks is angularly tiltable with respect to a transversal centerline plane (π) of the forming tunnel for varying the height of the tunnel in the longitudinal direction; and that each of the lower and upper supporting tracks (23, 24) of the gas permeable conveyor belts (21, 22) comprises a respective displacing group of the lower conveyor belt and of the upper conveyor belt, each displacing group of the lower and upper gas permeable conveyor belts (21, 22) being arranged at the sintering section; and wherein each of said displacing groups of the lower and upper gas permeable conveyor belts (21, 22) comprises a supporting and displacing belt substantially of the track type, said supporting and displacing belt being in contact and substantially translationally integral with the respective lower or upper gas permeable conveyor belt (21, 22). a) a loading section of a loose mass of granules made of expandable plastic material; b) a sintering section of said continuous element made of expanded plastic material, extending downstream of said loading section; c) a stabilizing section of said continuous element made of expanded plastic material, extending downstream of said sintering section; d) a forming tunnel extending along said sintering and stabilizing sections and defined between a pair of lateral walls (19, 20) and a pair of gas permeable conveyor belts (21, 22), respectively lower and upper, said belts (21, 22) being supported by respective lower and upper supporting tracks (23, 24); wherein at least one of the supporting tracks (23, 24) of the gas permeable conveyor belts (21, 22) comprises at least one portion extending in the sintering section, characterized by, that at least one of the supporting tracks is angularly tiltable with respect to a transversal centerline plane (π) of the forming tunnel for varying the height of the tunnel in the longitudinal direction; and that each of the lower and upper supporting tracks (23, 24) of the gas permeable conveyor belts (21, 22) comprises a respective displacing group of the lower conveyor belt and of the upper conveyor belt, each displacing group of the lower and upper gas permeable conveyor belts (21, 22) being arranged at the sintering section; and wherein each of said displacing groups of the lower and upper gas permeable conveyor belts (21, 22) comprises a supporting and displacing belt substantially of the track type, said supporting and displacing belt being in contact and substantially translationally integral with the respective lower or upper gas permeable conveyor belt (21, 22).