An electro-optic modulator includes a waveguide of a nonlinear optical material and an electrode line for generating an electrical field in a modulating region of the waveguide when a voltage is applied to the electrode line, thereby modulating light passing through the waveguide. Therein, the forward electro-optic response of the modulating region is the same as the backward electro-optic response; and the electro-optic response has a band-pass or a low-pass characteristic. A distance measuring device includes a light source emitting light, and such an electro-optic modulator arranged such that the emitted light passes through the electro-optic modulator in a first direction before being emitted from the distance measuring device, and after being reflected from a target passes through the electro-optic modulator in a second direction which is opposite to the first direction.