A projection device is provided for finally displaying a clear desired target image while shortening time until the target image is displayed, the projection device including: a light source; a spatial modulation element reflecting light from the light source by a display unit displaying a phase distribution of a target image; a modulation element control means that performs, in parallel by different arithmetic units, first processing of generating a phase distribution of the target image and second processing of generating a phase distribution of the target image by processing with a calculation cost higher than the first processing, and displays a phase distribution generated by the second processing on a display surface of the spatial modulation element after displaying a phase distribution generated by the first processing on a display surface of the spatial modulation element; and a projection means that projects reflected light from the spatial modulation element.