An assembled structure includes an electronic component, a heat-dissipating device and a stepped isolation member. The electronic component has a first perforation. The heat-dissipating device has a second perforation corresponding to the first perforation of the electronic component. The stepped isolation member includes a first segment, a second segment and a third segment. The outer diameter of the first segment is smaller than the outer diameter of the second segment, and the outer diameter of the second segment is smaller than the outer diameter of the third segment. The first segment is partially accommodated within the first perforation of the electronic component, the second segment is arranged between the first segment and the third segment and engaged with the second perforation of the heat-dissipating device, and the third segment is contacted with the heat-dissipating device.