An optical modulator includes an optical waveguide (32), a modulating electrode (33), a conductive layer (34), an electric signal input section (35), and connector members (36a,36b). At least a portion of the optical waveguide (32) is made of an electro-optic material. The modulating electrode (33) includes a first conductor line (33a), a second conductor line (33b) and a third conductor line (33c), which are coupled together electromagnetically, and applies a modulating electric field to a portion of the optical waveguide (32). The conductive layer (34) forms a first microstrip line with the first conductor line (32a), a second microstrip line with the second conductor line (33b) and a third microstrip line with the third conductor line (33c), respectively. Through the electric signal input section (35), an RF modulating signal is supplied to the modulating electrode (33). The connector members (36a,36b) connect the first, second and third conductor lines (33a,b,c) together at both ends. In this optical modulator, the first, second and third conductor lines (33a,b,c,) function as an odd-mode resonator for the RF modulating signal.