The support device for a rotating shaft of a solar tracker comprises a support plate (2) fixed to an upper end of a support column (1), and a clamp (3) comprising a lower clamp section (4) with a foot (7) fixed to the support plate (2) by means of screws (43) and an arcuate seat (9) for a bearing (52), and first and second opposite side clamp sections (5, 6) having upper ends at which there are arranged respective connecting elements (10, 11) connectable in an articulated manner to one another and lower ends at which there are arranged respective fixing and clamping elements (12, 13) configured for fitting onto the foot (7) and for being tightened against one another and against the lower clamp section (4) by means of a tightening screw (14).