Provided are a projection device and a projection-type video display device capable of displaying a plurality of videos, allowing speckles to be inconspicuous, and miniaturizing an optical system. A projection device includes an optical element including light diffusion elements capable of diffusing light, an irradiation device configured to irradiate the optical element with illumination light beams, each illumination light beam scanning the corresponding light diffusion element, spatial light modulators, each spatial light modulator being illuminated with illumination light beam which is incident from the irradiation device to each light diffusion element to be diffused, and projection optical systems, each projection optical system projecting modulation image obtained on each spatial light modulator on corresponding screen. The illumination light beam, which is incident to each position of each light diffusion element to be diffused, overlappedly illuminates on corresponding spatial light modulator.