A device for heating and connecting sheets (11, 12, 111, 121) of bituminous or synthetic membranes (100), comprising at least one sheet (11, 12, 111, 121) of a bituminous or synthetic membrane (100) which is applied to at least one base layer (141), said membrane (100) being formed with a single compound or having at least one bottom layer including a compound or a bituminous mixture and at least one upper layer including a polymeric material and an electrically conductive material, which is heated; in particular, a body (13, 23) having a mainly longitudinal (A) development and placed on a first edge (11a, 21a) of a first sheet (11, 21, 111, 121) of the membrane (100) in order to connect said first edge to a second edge (12a, 22a) of a second sheet (12, 22, 111, 121) of the membrane (100) is provided with an upper face (13a, 23a).