A wireless charging device includes a casing, a transmitter driving board and a transmitter coil assembly. The wireless charging device is used for charging a receiver coil of a mobile device. The transmitter driving board generates a first heat source. The transmitter driving board has a first thermal resistance. The transmitter coil assembly generates a second heat source. The transmitter coil assembly has a second thermal resistance. There is an interfacial thermal resistance between the transmitter coil assembly and the transmitter driving board. A product of a power dissipation of the second heat source and the second thermal resistance is lower than 15. The interfacial thermal resistance is higher than or equal to two times the first thermal resistance. A product of a power dissipation of the first heat source and the first thermal resistance is lower than or equal to 80.