A deicing device for propfan-type aircraft propulsion unit blades, wherein the propulsion unit includes a turbomachine that drives in rotation at least one rotor including a plurality of blades arranged around an annular crown moving with the blades, which forms with its outer wall part of an outer envelope of the propulsion unit, the outer envelope being subjected to atmospheric conditions outside the propulsion unit, the turbomachine generating a flow of hot gases that exit via an annular vein, which is concentric with the moving annular crown, and defined for part of its surface by the inner wall of the moving annular crown. The deicing device includes: a mechanism capturing thermal energy from the annular vein, within the moving annular part; a mechanism transferring thermal energy towards the rotor blades; and a mechanism distributing the thermal energy onto at least a part of the surface of the blades.