Hybrid-type rotorcraft, comprising: • a main rotor providing at least all or part of a lift of said rotorcraft, • at least two propulsion elements (2, 2') providing all or part of a propulsion of said rotorcraft, said two propulsion elements (2, 2') each being mounted on a particular half-wing (3, 3'), said half-wings (3, 3') being arranged symmetrically on either side of an anteroposterior median plane XOZ of symmetry of all or part of said rotorcraft, said anteroposterior median plane XOZ extending between a front region and a rear region of said rotorcraft in a longitudinal direction X and between a lower region and an upper region of said rotorcraft in an elevation direction Z, • a horizontal stabiliser (8, 28) arranged in said rear region of said rotorcraft on either side of said anteroposterior median plane XOZ, and • two fins (11-51, 11'-51') arranged on respective sides of said anteroposterior median plane XOZ, said two fins (11-51, 11'-51') consisting of a left fin positioned at the level of a left distal region of said horizontal stabiliser (8, 28) and a right fin (11'-51') positioned at the level of a right distal region of said horizontal stabiliser (8, 28), each of said two left/right fins (11-51, 11'-51') comprising a lower left/right fin aerofoil (12-52, 12'-52') arranged below said horizontal stabiliser (8, 28) and an upper left/right fin aerofoil (13-53, 13'-53') arranged above said horizontal stabiliser (8, 28), said two left lower/upper fin aerofoils (12-52, 13-53) and said two right lower/upper fin aerofoils (12'-52', 13'-53') being rigidly secured to said horizontal stabiliser (8, 28), characterised in that said lower left fin aerofoil approaches said upper left fin aerofoil from its particular joining point with said horizontal stabiliser (8, 28) and said lower right fin aerofoil (12'-52') approaches said upper right fin aerofoil (13'-53') from its particular joining point with said horizontal stabiliser (8, 28), said two left lower/upper fin aerofoils (12-52, 13-53) deviating completely or partly, at least at their free ends (16-56, 17-57), from said anteroposterior median plane XOZ and said two right lower/upper fin aerofoils (12'-52', 13'-53') deviating completely or partly, at least at their free ends (16'-56', 17'-57'), from said anteroposterior median plane XOZ. • a main rotor providing at least all or part of a lift of said rotorcraft, • at least two propulsion elements (2, 2') providing all or part of a propulsion of said rotorcraft, said two propulsion elements (2, 2') each being mounted on a particular half-wing (3, 3'), said half-wings (3, 3') being arranged symmetrically on either side of an anteroposterior median plane XOZ of symmetry of all or part of said rotorcraft, said anteroposterior median plane XOZ extending between a front region and a rear region of said rotorcraft in a longitudinal direction X and between a lower region and an upper region of said rotorcraft in an elevation direction Z, • a horizontal stabiliser (8, 28) arranged in said rear region of said rotorcraft on either side of said anteroposterior median plane XOZ, and • two fins (11-51, 11'-51') arranged on respective sides of said anteroposterior median plane XOZ, said two fins (11-51, 11'-51') consisting of a left fin positioned at the level of a left distal region of said horizontal stabiliser (8, 28) and a right fin (11'-51') positioned at the level of a right distal region of said horizontal stabiliser (8, 28), each of said two left/right fins (11-51, 11'-51') comprising a lower left/right fin aerofoil (12-52, 12'-52') arranged below said horizontal stabiliser (8, 28) and an upper left/right fin aerofoil (13-53, 13'-53') arranged above said horizontal stabiliser (8, 28), said two left lower/upper fin aerofoils (12-52, 13-53) and said two right lower/upper fin aerofoils (12'-52', 13'-53') being rigidly secured to said horizontal stabiliser (8, 28), characterised in that said lower left fin aerofoil approaches said upper left fin aerofoil from its particular joining point with said horizontal stabiliser (8, 28) and said lower right fin aerofoil (12'-52') approaches said upper right fin aerofoil (13'-53') from its particular joining point with said horizontal stabiliser (8, 28), said two left lower/upper fin aerofoils (12-52, 13-53) deviating completely or partly, at least at their free ends (16-56, 17-57), from said anteroposterior median plane XOZ and said two right lower/upper fin aerofoils (12'-52', 13'-53') deviating completely or partly, at least at their free ends (16'-56', 17'-57'), from said anteroposterior median plane XOZ.