Illumination device and steering device using the same

An illumination device for emitting light in directions centered on a first direction, the illumination device comprising:

• a light source configured to emit light centered on a second direction, the second direction being different from the first direction;
• and
• a light guiding path on which the light from the light source is incident that includes, at a part of an outer periphery thereof on a side opposite to the light source, a boundary surface reflecting the light incident in the second direction toward the first direction, wherein
• in the boundary surface by which the light emitted from the light source in the second direction is reflected toward the first direction,
• a first angle serving as an incident angle at a first point on the boundary surface satisfies a total reflection condition,
• an angle formed by a normal line on the boundary surface with respect to the second direction is defined as an inclination angle, and
• for light inclined by a predetermined displacement angle from the second direction toward the first direction being reflected by the boundary surface toward the first direction among the light emitted from the light source, a second angle serving as the inclination angle formed at a second point on the boundary surface is smaller than the first angle, and a deviation between the first angle and the second angle is equal to or less than the displacement angle.