Toner set and full-color image-forming method suitable for use of the toner set

A full-color image-forming method comprising the steps of:

• forming respective toner images of yellow toner, magenta toner and cyan toner on an intermediate transfer member;
• and
• superposing toner-images of back toner on the formed toner images so that the black toner-images are positioned as a highest upper-part on the intermediate transfer member;
• transferring the superposed toner images to a recording medium, wherein
• the black toner comprises black toner particles comprising at least a binder resin and a black colorant and having a standard deviation of degree of roundness of not more than 0.045;
• the yellow toner comprises yellow toner particles comprising at least a binder resin and a yellow colorant and having a standard deviation of degree of roundness of not more than 0.045 and an average degree of roundness larger than that of the black toner particles,
• the magenta toner comprises magenta toner particles comprising at least a binder resin and a magenta colorant and having a standard deviation of degree of roundness of not more than 0.045 and an average degree of roundness larger than that of the black toner particles,
• the cyan toner comprises cyan toner particles comprising at least a binder resin and a cyan colorant and having a standard deviation of degree of roundness of not more than 0.045 and an average degree of roundness larger than that of the black toner particles, and
• wherein the binder resin contained respectively in the yellow toner particles, the magenta toner particles and the cyan toner particles has a glass transition point ranging from 55 to 75° C., a softening point ranging from 95 to 120° C., a number-average molecular weight ranging from 2,500 to 6,000 and a ratio of weight-average molecular weight/number-average molecular weight of 2 to 8.