An object of the invention is to miniaturize a projection display device, enhance reliability of the device, and reduce speckle noise. A blue laser (1), a red laser (2), and a green laser (3) emit blue laser light, red laser light, and green laser light, respectively. A spatial light modulation element (14) modulates the blue laser light emitted from the blue laser (1), the red laser light emitted from the red laser (2), and the green laser light emitted from the green laser (3). A projection lens (15) projects the laser light modulated by the spatial light modulation element (14) onto a screen. First and second light diffusing elements (8 and 9) are arranged on an optical axis between the blue laser (1), the red laser (2), and the green laser (3); and the spatial light modulation element (14) to change the degree of diffusion of the blue laser light, the red laser light, and the green laser light temporally and electrically.