An image reading device includes a lens mirror array, a photoelectric conversion section, and a diaphragm section. The lens mirror array includes a plurality of optical elements. Each of the optical elements includes an incident-side lens surface, an upstream-side reflection surface, a downstream-side reflection surface, an emission-side lens surface, and a stray light reflection surface. The incident-side lens surface transmits and converges reflected light from a read surface. The upstream-side reflection surface reflects light made incident via the incident-side lens surface. The downstream-side reflection surface reflects the light. The emission-side lens surface transmits and converges the light and images the light on an imaging surface. The stray light reflection surface reflects stray light. The photoelectric conversion section receives, photoelectrically converts, and outputs the reflected light. The diaphragm section is disposed between the read surface and the incident-side lens surface and includes a slit-like opening section.