A processing device, a sheet manufacturing apparatus, a processing method, and a sheet manufacturing method enable quickly removing color material when color material is contained in a material containing fiber. A processing device has a defibrator configured to defibrate, in air, fibrous material containing fiber; and a particle supply device configured to supply particles of dry ice to the material containing fiber during defibration or after defibration. The material containing fiber contains color material; and the particles work to separate the color material for the fibers by colliding with the color material contained in the material containing fiber.