Transfer device installable on a structure, adapted to facilitate the loading and unloading of a load, comprising a support structure, configured to be fixed to the floor of the structure, whereto, in an at least translatable manner, a platform is constrained whereon said load is positioned during the loading and unloading operations, which - it is movable at least from a deposit position, wherein said platform is at the level of the ground to an access position, wherein said platform is at the level of said floor and vice versa always keeping substantially horizontal; - has side safety barriers (7; 700) coupled to the sides of said platform; - has a front safety barrier (6; 600) rotatably constrained according to a horizontal axis (62; 602) to the said platform so that from a substantially vertical set-up where it serves as a barrier may rotate to serve as a ramp; characterised in that: - each of said side safety barriers (7; 700) comprises: - an articulated quadrilateral (72; 702) of which an arm consists of the corresponding side edge of said platform while the opposed arm (74; 704) constitutes the railing (74; 704) of the same side barrier (7; 700), - a side ramp (71; 701) constrained to said railing (74; 704) or substantial part of the same; and in that: - sliding means capable of sliding on the ground are connected: - with first kinematic mechanisms (8, 85, 63, 61; 703) to the said front safety barrier (6; 600), - with second kinematic mechanisms (8, 73; 600) to the said side safety barriers (7; 700), - said first (8, 85, 63, 61; 703) and second (8, 73; 600) kinematic mechanisms being adapted to bring said platform from locking to unlocking set-up and vice versa when the said sliding means are pressed/detached against/from said ground from the same platform that goes down/lifts where by locking/unlocking set-up it is meant a set-up wherein said front (6; 600) and side (7; 700) safety barriers respectively allow/prevent the exit of said load from said platform through the correspondent edges. - it is movable at least from a deposit position, wherein said platform is at the level of the ground to an access position, wherein said platform is at the level of said floor and vice versa always keeping substantially horizontal; - has side safety barriers (7; 700) coupled to the sides of said platform; - has a front safety barrier (6; 600) rotatably constrained according to a horizontal axis (62; 602) to the said platform so that from a substantially vertical set-up where it serves as a barrier may rotate to serve as a ramp; - each of said side safety barriers (7; 700) comprises: - an articulated quadrilateral (72; 702) of which an arm consists of the corresponding side edge of said platform while the opposed arm (74; 704) constitutes the railing (74; 704) of the same side barrier (7; 700), - a side ramp (71; 701) constrained to said railing (74; 704) or substantial part of the same; - an articulated quadrilateral (72; 702) of which an arm consists of the corresponding side edge of said platform while the opposed arm (74; 704) constitutes the railing (74; 704) of the same side barrier (7; 700), - a side ramp (71; 701) constrained to said railing (74; 704) or substantial part of the same; - sliding means capable of sliding on the ground are connected: - with first kinematic mechanisms (8, 85, 63, 61; 703) to the said front safety barrier (6; 600), - with second kinematic mechanisms (8, 73; 600) to the said side safety barriers (7; 700), - with first kinematic mechanisms (8, 85, 63, 61; 703) to the said front safety barrier (6; 600), - with second kinematic mechanisms (8, 73; 600) to the said side safety barriers (7; 700), - said first (8, 85, 63, 61; 703) and second (8, 73; 600) kinematic mechanisms being adapted to bring said platform from locking to unlocking set-up and vice versa when the said sliding means are pressed/detached against/from said ground from the same platform that goes down/lifts where by locking/unlocking set-up it is meant a set-up wherein said front (6; 600) and side (7; 700) safety barriers respectively allow/prevent the exit of said load from said platform through the correspondent edges.