Disclosed is a locking device, comprising an outer sleeve (1) and at least one locking unit (2) located in the outer sleeve (1), wherein the locking unit (2) is formed by connecting a plurality of pressing blocks (3), a gap (5) is provided between two adjacent ones of pressing blocks (3), a rod locking hole (6) is provided in the gap (5), and a set screw hole (7) is provided on the outer sleeve (1) at a position corresponding to the locking unit (2); and when a set screw is screwed into the set screw hole (7) to directly or indirectly press the locking unit (2), the locking unit (2) deforms and drives the pressing blocks (3) to tightly press rods (8, 9) mounted in the respective rod locking holes (6) at the same time.