A multimedia device comprises a host, which comprises a connection unit, a control unit for controlling connection of the connection unit to an external mobile electronic device to charge the connected mobile electronic device and to transmit multimedia music from the connected mobile electronic device to a FM channel of a car audio radio system for broadcasting, and a display unit controllable by the control unit to display the current operation status of the control unit, and a holder member coupled to the host and radially adjustable for securing the host to a cup holder for motor vehicle.