A fixing structure of a pull-out faucet is mounted on a platform with a fixing hole and contains a pull-out faucet including a housing, a pull-out spray head, a mixing valve, and a pipe line set; the pipe line set including a plurality of fixedly static pipe lines and a movably dynamic pipe line; a positioning device including a seat and a clamping set; the seat being fixed under the platform by the clamping set and being fixed in the fixing hole to fit with the housing, the seat including a passage set for inserting the pipe line set; wherein the passage set has a first passage for inserting the static pipe lines and a second passage for inserting the dynamic pipe line, and the first passage is spaced apart from the second passage so that the dynamic pipe line is limited in the second passage to move smoothly.