An air-jet type spinning device (4), comprising a body (8) at least partially hollow which defines a spinning chamber (12), a fibre feeding device (16) that feeds fibres into the spinning chamber (12), and a spinning spindle (20) including a spinning channel (24) for the suction of yarn obtained from the fibres. The device (4) including at least one channel (28) for sending a jet of compressed air inside the spinning chamber (12). A flow amplifier (32) comprising an expansion chamber (36) is in fluidic connection with the outside of the body (8), wherein the at least one channel (28) comes out in an emission point (40) inside the expansion chamber (36), to introduce compressed air at an inlet cross-section (44). The expansion chamber (36) comprises an outlet mouth (48), fluidically connected to the spinning chamber (12) and having an outlet cross-section (52) smaller than the inlet cross-section (44).