A jointing device for connecting two superimposed mast members of a tower crane, in particular for detachably connecting a lower mast member to an upper mast member, the jointing device comprising: - a top portion (8.1) which is located at the top of a lower corner chord member (3.1) and which extends a lower mast member, - a base portion (8.2) which is located at the base of a corresponding upper corner chord member (3.2) and which extends an upper mast member, and - at least two connecting pins (10, 11) removable and respectively oriented according to a first direction and a second direction substantially orthogonal to each other, the jointing device being characterized in that: - the top portion (8.1) comprises two primary joint bars secured to two primary outer faces (14.1) which are vertical, opposite each other and defined by the lower corner chord member (3.1), each primary joint bar protruding above the top of the lower corner chord member (3.1), each primary joint bar having coaxial primary orifices (15.1); - the top portion (8.1) comprises two secondary joint bars secured to two secondary outer faces (16.1) which are vertical, opposite each other and defined by the lower corner chord member (3.1), each secondary joint bar protruding above the top of the lower corner chord member (3.1), each secondary joint bar having coaxial secondary orifices (17.1), the center point of each primary orifice (15.1) being located, relative to the top of the respective lower corner chord member (3.1), at a primary height (H15.1) different from the secondary height (H17.1) at which the center point of a respective secondary orifice (17.1) is located; - the base portion (8.2) is formed by a tubular base of an upper corner chord member (3.2) of the upper mast member, said base portion (8.2) being disposed between the primary joint bars and between the secondary joint bars, - the base portion (8.2) having primary holes (15.2) and secondary holes (17.2) which open out respectively on outer faces (14.2, 16.2) of the upper corner chord member (3.2) which are vertical and opposite the upper corner chord member (3.2), the primary holes (15.2) and the secondary holes (17.2) being arranged to coincide in alignment respectively with the primary orifices (15.1) and with the secondary orifices (17.1), such that a connecting pin passes through each primary orifice (15.1) and each primary hole (15.2) and that the other connecting pin passes through each secondary orifice (17.1) and each secondary hole (17.2), - the jointing device further comprises primary plates and secondary plates which are respectively secured against primary inner faces and secondary inner faces defined by the upper corner chord member (3.2), the primary plates and secondary plates being shaped to contribute respectively to the support bearing surface of the connecting pins (10,11). - a top portion (8.1) which is located at the top of a lower corner chord member (3.1) and which extends a lower mast member, - a base portion (8.2) which is located at the base of a corresponding upper corner chord member (3.2) and which extends an upper mast member, and - at least two connecting pins (10, 11) removable and respectively oriented according to a first direction and a second direction substantially orthogonal to each other, the jointing device being characterized in that: - the top portion (8.1) comprises two primary joint bars secured to two primary outer faces (14.1) which are vertical, opposite each other and defined by the lower corner chord member (3.1), each primary joint bar protruding above the top of the lower corner chord member (3.1), each primary joint bar having coaxial primary orifices (15.1); - the top portion (8.1) comprises two secondary joint bars secured to two secondary outer faces (16.1) which are vertical, opposite each other and defined by the lower corner chord member (3.1), each secondary joint bar protruding above the top of the lower corner chord member (3.1), each secondary joint bar having coaxial secondary orifices (17.1), the center point of each primary orifice (15.1) being located, relative to the top of the respective lower corner chord member (3.1), at a primary height (H15.1) different from the secondary height (H17.1) at which the center point of a respective secondary orifice (17.1) is located; - the base portion (8.2) is formed by a tubular base of an upper corner chord member (3.2) of the upper mast member, said base portion (8.2) being disposed between the primary joint bars and between the secondary joint bars, - the base portion (8.2) having primary holes (15.2) and secondary holes (17.2) which open out respectively on outer faces (14.2, 16.2) of the upper corner chord member (3.2) which are vertical and opposite the upper corner chord member (3.2), the primary holes (15.2) and the secondary holes (17.2) being arranged to coincide in alignment respectively with the primary orifices (15.1) and with the secondary orifices (17.1), such that a connecting pin passes through each primary orifice (15.1) and each primary hole (15.2) and that the other connecting pin passes through each secondary orifice (17.1) and each secondary hole (17.2), - the jointing device further comprises primary plates and secondary plates which are respectively secured against primary inner faces and secondary inner faces defined by the upper corner chord member (3.2), the primary plates and secondary plates being shaped to contribute respectively to the support bearing surface of the connecting pins (10,11).