A method for fixing a full color toner image by inserting a transfer medium to which a toner image is transferred, between a pair of rolls of a fixing apparatus, and pressing the medium therebetween, wherein the toner image is formed of a full color toner prepared by dispersing a colorant into a polyester resin containing a diol component represented by the following general formula (I) as a constituent and having a softening point of 100.degree. to 120.degree. C., as measured by a ring and ball method, a glass transition temperature of 55.degree. C. or more, a Gardner color scale of 2 or less and a haze value of 15 or less, and the fixing operation is conducted while supplying a functional group-containing organopolysiloxane having a viscosity of 10 to 100,000 cs at 25.degree. C. to a roll in contact with the toner image, whereby the full color toner image can be stably fixed without wrapping of the transfer medium around the roll and offset, and the fixed image having good image quality can be obtained: ##STR1## wherein R represents an ethylene group or a propylene group, each of x and y is an integer of 1 or more, and x+y is 2 to 6.