A light emitting device capable of achieving a small exit area, high directivity, and low loss; a manufacturing method thereof; an illumination device using this light emitting device; and a projector are provided. The light emitting devices 16 include an LED (light emitting element) 25, in the form of a rectangular light emitting element, having a light emitting part 23 for emitting illumination light; a substrate 26 for fixing the LED 25; a spacer 27 having a mirror surface 27A for reflecting the illumination light emitted from the LED 25; and a tapered rod (columnar light guide unit) 28 having a device-side incident surface (incident surface) 28A upon which illumination light is incident, tapered-rod side surfaces 28B serving as total reflection surfaces for totally reflecting illumination light received from the device-side incident surface 28A, and the device-side exit surface (exit surface) 28C which has a larger area than the device-side incident surface 28A and which emits the illumination light totally reflected at the tapered-rod side surfaces 28B.