Multistage socket

A multistage socket including a main body having a disc section. Multiple fixing blocks are disposed on one face of the disc section at equal angular intervals. A movable block is arranged between each two adjacent fixing blocks. The inner end faces of the movable blocks facing the center of the disc section define a polygonal hole. The movable blocks are resiliently movable toward or away from the center of the disc section. A rotary member is rotatably fitted around the disc section of the main body. Multiple arced guide sections are symmetrically formed on an inner face of the rotary member corresponding to the movable blocks. Each arced guide section has multiple recessed arced faces with different thickness. When rotating the rotary member, the outer ends of the movable blocks can abut against the opposite recessed arced faces of the arced guide sections with the same thickness. Therefore, the movable blocks can be located in different recessed arced faces to vary the distance between the movable blocks and the center of the disc section so as to adjust the size of the polygonal hole in accordance with the sizes of different nuts or bolts.