The light source device of the projection display apparatus according to the present disclosure includes: solid-state light sources that individually emit blue light, green light, and red light; a plurality of dichroic mirrors that combine the blue light, the green light, and the red light having exited from the solid-state light sources; a first diffusion plate on which the combined light having been combined by the plurality of dichroic mirrors is incident; a dynamic diffusion plate that is disposed at a position at which the combined light having exited from the first diffusion plate converges and starts to diverge.