The present invention provides a cerium oxide slurry, a cerium oxide polishing slurry, and a method of polishing a substrate by using the same, wherein decrease of scratches and polish at high speed can be realized by reducing the content of coarse grains by improving in the disperse state of cerium oxide particles. The invention relates to a cerium oxide slurry containing cerium oxide particles, dispersant and water, in which the ratio of weight of cerium oxide/weight of dispersant is in a range of 20 to 80 and relates a cerium oxide polishing slurry comprising the cerium oxide slurry and additives such as a water-soluble polymer.