An assembly device applicable to assembling an isolation cover to a main body of a circuit board is provided. The main body and the isolation cover respectively have a plurality of first positioning portions and a plurality of second positioning portions corresponding to each other. The second positioning portions correspondingly pass through the first positioning portions, respectively. The assembly device includes a base, a press-fitting mechanism movably connected to the base, and a drive mechanism disposed at the base. The base has a supporting portion for disposing the isolation cover and the main body. The press-fitting mechanism has a press-fitting portion facing the supporting portion. The drive mechanism has a drive portion connected to the press-fitting mechanism, for driving the press-fitting mechanism to move towards the supporting portion of the base via the drive portion, so as to bend and fasten ends of the second positioning portions.