The planetary centrifugal mixer comprises a fixed axis (4) on which is rotatably mounted an arm (10) carrying a fixed rod (11) extending upwardly. The arm (10) is rotated about the axis (4) by means of a drive pinion (9), and at the same time a mixing bowl (22) fitted on the rod (11) is rotated about said rod, the drive pinion (16) of the bowl (22) being coupled by means of an intermediate pinion (18) to a pinion (19) integral with the fixed axis (4). The side wall (24) of the bowl (22) has at least two segments (28), the curvature radius being greater than that of the remaining segments (27); a central guide (29) projects from the bottom (23) of the bowl (22), its outer shape being matched to the shape of the lateral wall (24).