An optical modulator with FPC and optical transmission device using the same are provided. This optical modulator includes a flexible printed circuit which electrically connects the optical modulator to a circuit board. The flexible printed circuit has a substantially quadrilateral shape. A pad is formed on the flexible printed circuit along one side of the substantially quadrilateral shape so as to be electrically connected to the circuit board. In order to release the mechanical stress applied onto the side or the end portion of the flexible printed circuit and/or to prevent propagation of distortion generated in the side or the end portion, the flexible printed circuit has: a cutout or a notch provided in a direction from a part of at least one side toward the inside of the flexible printed circuit; and/or a curved portion connecting at least two adjacent sides.