A nut disassembling device is provided, comprising an adjustment member, a support rod, a center pillar and two clamping blocks. The support rod is screwed with two tightening members. Each of the tightening members is rotatable relative to the support rod, and the clamping block is moved by the tightening member. Thus, during the clamping of the nut, the clamping blocks close and push the nut through rotation of the tightening members, and it effectively improves the clamping for installation and uninstallation of the nut.