An endoscope illumination device includes: an illumination optical system including an entrance surface disposed along a circumferential direction centered on a predetermined axis and provided at one-end side in the direction of the predetermined axis, an emission surface positioned at an outermost side in a radial direction with respect to the predetermined axis and radially emitting illumination light entering from the entrance surface, a diffusion surface disposed at an intermediate position of an optical path of the illumination light between the entrance surface and the emission surface and transmitting and diffusing the illumination light； and a light emitting portion disposed closer to the one-end side than the entrance surface is and emitting, toward the entrance surface, the illumination light substantially in the direction of the axis.
