Air-jet type spinning device comprising - a body at least partially hollow, which delimits a spinning chamber - a fibre feeding device , facing said spinning chamber so as to feed the fibres into the spinning chamber , wherein the fibre feeding device is connected with the outside through a suction mouth , - a spinning spindle at least partially inserted in the spinning chamber and fitted with a spinning channel for the suction of yarn obtained from said fibres, the spinning channel defining a spinning direction (X-X), - at least one channel for sending a jet of compressed air to be sent inside the spinning chamber characterised in that - the body comprises a flow amplifier comprising an expansion chamber , in fluidic connection with the outside of the body , through the suction mouth which is fluidically connected to the spinning chamber through an air intake channel , - wherein the at least one channel comes out in an emission point inside the expansion chamber , to introduce compressed air at an inlet cross-section of the expansion chamber , measured in relation to a cross-section plane (S-S) perpendicular to said spinning direction (X-X), - wherein the expansion chamber comprises an outlet mouth , fluidically connected to the spinning chamber and having an outlet cross- section smaller than said inlet cross- section , said outlet cross-section being measured relative to a cross-section plane (S-S) perpendicular to said spinning direction(X-X), - said outlet mouth being shaped so as to present a profile shaped to create an outlet path of the air parallel to said profile by means of the Coand effect. - a body at least partially hollow, which delimits a spinning chamber - a fibre feeding device , facing said spinning chamber so as to feed the fibres into the spinning chamber , wherein the fibre feeding device is connected with the outside through a suction mouth , - a spinning spindle at least partially inserted in the spinning chamber and fitted with a spinning channel for the suction of yarn obtained from said fibres, the spinning channel defining a spinning direction (X-X), - at least one channel for sending a jet of compressed air to be sent inside the spinning chamber characterised in that - the body comprises a flow amplifier comprising an expansion chamber , in fluidic connection with the outside of the body , through the suction mouth which is fluidically connected to the spinning chamber through an air intake channel , - wherein the at least one channel comes out in an emission point inside the expansion chamber , to introduce compressed air at an inlet cross-section of the expansion chamber , measured in relation to a cross-section plane (S-S) perpendicular to said spinning direction (X-X), - wherein the expansion chamber comprises an outlet mouth , fluidically connected to the spinning chamber and having an outlet cross- section smaller than said inlet cross- section , said outlet cross-section being measured relative to a cross-section plane (S-S) perpendicular to said spinning direction(X-X), - said outlet mouth being shaped so as to present a profile shaped to create an outlet path of the air parallel to said profile by means of the Coand effect. <EOS>