A communication device is capable of extending a power supply unit to a second casing without additional components. A mobile telephone includes a circuit board disposed at an operation unit-side casing, a circuit board disposed at a display unit-side casing, a circuit part formed on the circuit board having a ground pattern and a contact point, a reference potential pattern layer disposed at the operation unit-side casing and electrically connected to the ground pattern, a reference potential pattern layer disposed at the display unit-side casing, and an FPC unit. The FPC unit includes a signal line and a shield layer. The shield layer is electrically connected to the contact point in the operation unit-side casing and is thus electrically connected to the reference potential pattern layer in the display unit-side casing.