A toner set is composed of toners of a plurality of colors that are used in a tandem-type color image forming apparatus. Each of the toners of a plurality of colors includes toner base particles and an external additive. The external additive includes small-diameter silica particles and large-diameter silica particles larger than the small-diameter silica particles. When, of the toners of a plurality of colors, three color toners to be used consecutively for forming the toner image are defined as a first toner, second toner and third toner respectively in order of usage thereof, the average particle diameter of the large-diameter silica particles contained in the second toner is smaller than the average particle diameter of the large-diameter silica particles contained in the first toner and is larger than the average particle diameter of the large-diameter silica particles contained in the third toner.