An exemplary embodiment of an electronic device includes a cover including a first hole, and a heat dissipating assembly. The heat dissipating assembly includes a movable board including a second hole and slidably connected to the cover, and a heat magnifying device received inside the cover and adjacent to a heat element. The heat magnifying device includes a moving end secured with the movable board. When the heat element is maintained room temperature, the first hole and the second hole are staggered from each other to seal the cover. When heat generated by the heat element heats the heat magnifying device and causes the moving end of the heat magnifying device to move under thermal expansion and drive the movable board to slide relatively to the cover, and the first hole of the cover and the second hole of the movable board are communicated with each other.