To provide an electric field absorbing optical modulator to improve a high frequency property by a design for adjusting a characteristic impedance of a transmission line.

The electric field absorbing optical modulator has an electric field absorbing optical modulating element 1, the transmission line 4 for supplying a high frequency signal to the optical modulating element, an impedance conductor 9 connected to the transmission line 4 at a branching point P and the electric field optical modulating element 1, and a terminating resistor 8 connected to an terminated end q of the transmission line 4. The electric field absorbing optical modulator comprises a part of an input end side of the transmission line for increasing the characteristic impedance as approaching from the input end to the branching point p, and a part of a terminated end side of the transmission line for maintaining or decreasing the characteristic impedance as approaching from the branching point p to the terminated end q.