An imaging apparatus in which an imaging head having an observation hole for intaking images of an object to be observed formed at a top end is exchangeably mounted to a main body having an imaging device and an illumination light source wherein the imaging head is provided with a plurality of optical fibers for guiding a light from the illumination light source and illuminating the same to the object, light incident ends of respective optical fibers are disposed at positions opposing to emission ends of the illumination light source, and the light emission ends are circularly disposed around the image pick-up optical axis, whereby an appropriate illumination light in accordance with a magnifying ratio can be illuminated without disposing an illumination light source such as of LEDs to an imaging head such as an exchangeable lens unit.