The optical modulator includes an optical waveguide for receiving light entered from a first end surface thereof and for emitting the light from a second end surface opposing to the first end surface, a flexible light transmitting member disposed so as to face with a boundary surface of the optical waveguide and has a gap between the flexible light transmitting member and the boundary surface of the optical waveguide and a modulation device for bringing the flexible light transmitting member into contact with the boundary surface of the optical waveguide. The image recording apparatus includes the above exposure head and a scanning device for relatively moving a photosensitive material and the exposure head.