A heat-dissipating casing for a communication apparatus accommodates a circuit board having a power element and includes an insulating case, a lid coupled to the insulating case, and a thermally conductive metal member. The insulating case has a receiving space, a first opening, and a second opening. The first and second openings communicate with the receiving space. The thermally conductive metal member is fixed to the inside of the insulating case, seals the second opening, and dissipates heat generated by the power element. The heat-dissipating casing is effective in dissipating heat, characterized by its low weight and low production costs, and conducive to protection and dust prevention.