A supporting seat includes a base adapted to be securely connected to the heat conductive plate, two arms extending obliquely from the base from two opposed sides of the base, two engagement plates each formed on a free end of a corresponding arm and adapted to engage with a bottom face of a lowermost one of the heat dissipating fins and multiple through holes defined through each of the two engagement plates for extension of the heat dissipating tubes. Weight of the heat dissipating fins is supported and deformation of the heat dissipating tubes is prevented.