Polishing device for inner side and outer side of bowl-shaped workpiece and polishing method of polishing device

The invention provides a polishing device for the inner side and the outer side of a bowl-shaped workpiece and a polishing method of the polishing device, and relates to the technical field of workpiece polishing. The polishing device comprises a sand changing assembly for placing abrasive paper, a moving assembly for moving the abrasive paper, an outer side polishing and fixing assembly and an inner side polishing and fixing assembly. The outer side grinding fixing assembly comprises a first fixing base, a first rotating base arranged on the first fixing base and a plurality of first clamping components circumferentially arranged on the first rotating base. The first clamping component is configured to be capable of being opened in the radial direction of the first rotating base so as to be connected to the bowl-shaped workpiece in a supporting mode. The inner side grinding fixing assembly comprises a second fixing base, a second rotating base rotationally arranged on the second fixing base, a plurality of s