Operation device and image reading apparatus

An operation device comprising:

• a panel including a light-transmissive portion having a ring-like shape;
• a light guide element having a first surface and a second surface, the first surface facing the panel;
• a plurality of light sources provided at locations around the light guide element;
• and
• a plurality of electrodes provided at locations corresponding to the light-transmissive portion closer to the second surface of the light guide element and configured to detect a capacitance,
• wherein the light guide element has a diffusion surface having a ring-like shape formed on the second surface,
• wherein the ring-like shape of the diffusion surface includes a first region corresponding to one of the light sources and a second region provided between two of the light sources adjacent to each other,
• wherein a distance from a location of the light-transmissive portion to a periphery of the ring close to the light source is greater in the second region than in the first region, and
• wherein light emitted from the light source and incident to the light guide element is diffusion-reflected on the diffusion surface and a part of the diffusion-reflected light illuminates the light-transmissive portion.