Magnetic field generator (1, 21, 27, 54, 55) for a magnetocaloric thermal appliance comprising a first (2, 22, 28) and a second (3, 23, 29) magnetizing structure each mounted in a frame (35, 36), opposite to each other, parallel, and arranged to define at least two diametrically opposite air gaps (42, 43, 49, 50, 51, 52), each magnetizing structure (2, 22, 28, 3, 23, 29) comprising a first (4, 24, 30) and a second (5, 25, 31) structurally identical magnetizing assemblies, diametrically opposite and arranged on either side of a ferromagnetic central part (6, 56), each first (4, 24, 30) and second (5, 25, 31) magnetizing assembly comprising a first (7, 32, 57), respectively a second (14, 33, 58), polygonal, uniformly magnetized central magnet comprising an active side (8, 45, 15, 47) on the side of the air gap and a passive side (9, 46, 16, 48), parallel with each other and comprising at least four sides, with the magnetic induction vector of each central magnet (7, 32, 14, 33) perpendicular to its active (8, 45, 15, 47) and passive (9, 46, 16, 48) sides, said other sides, called lateral sides of each central magnet (7, 32, 57, 14, 33, 58) being quadrangular, perpendicular to said active (8, 45, 15, 47) and passive (9, 46, 16, 48) sides and in contact with the sides called internal sides (11, 18) of a uniformly magnetized magnetic belt (13, 20) surrounding each central magnet (7, 14) and comprising external sides (12, 19) parallel to said internal sides (11, 18), the magnetic induction vectors in each magnetic belt (13, 20) being perpendicular to its internal sides (11, 18), said first and second magnetizing assemblies (4, 24, 30, 5, 25, 31) being connected to said ferromagnetic part (6, 56) by means of every corresponding magnetic belt (13, 20), characterized in that the first (2, 22, 28) and second (3, 23, 29) magnetizing structures are identical and arranged so that the active side (8, 45) of the first central magnet (7, 32, 57) of the first magnetizing structure (2, 22, 28) is opposite to the active side (15, 47) of the second central magnet (14, 33, 58) of the second magnetizing structure (3, 23, 29) and that the active side (15, 47) of the second central magnet (14, 33, 58) of the first magnetizing structure (2, 22, 28) is opposite to the active side (8, 45) of the first central magnet (7, 32, 57) of the second magnetizing structure (3, 23, 29), in that the magnetic induction vector of said first central magnet (7, 32, 57) is oriented towards its active side (8, 45) and the magnetic induction vectors in the magnetic belt surrounding said first central magnet (7, 32, 57) are directed towards its internal sides, in that the magnetic induction vector of said second central magnet (14, 33, 58) is oriented towards its passive side (16, 48) and the magnetic induction vectors in the magnetic belt surrounding said second central magnet (14, 33, 58) are directed towards its external sides, and in that the magnetic flux generated by said magnetic field generator (1, 21, 27, 55, 54) forms one single loop and circulates, in the first magnetizing structure (2, 22, 28), from the second (5, 25, 31) to the first (4, 24, 30) magnetizing assembly, in the second magnetizing structure (3, 23, 29), from the second (5, 25, 31) to the first (4, 24, 30) magnetizing assembly and, between the two magnetizing structures (2, 22, 28; 3, 23, 29), through said air gaps (42, 43, 49, 50, 51, 52), from the active side (8, 45) of the first central magnet (7, 32, 57) of the first magnetizing structure (2, 22, 28) to the active side (15, 47) of the second central magnet (14, 33, 58) of the second magnetizing structure (3, 23, 29) and from the active side (8, 45) of the first central magnet (7, 32, 57) of the second magnetizing structure (3, 23, 29) to the active side (15, 47) of the second central magnet (14, 33, 58) of the first magnetizing structure (2, 22, 28).