A method and a device are provided for replacing individual idler rollers for conveyors, with which a web belt can be lifted and worn-out or damaged idler rollers in upper and lower runs can be individually replaced. The device includes, separately for replacing the idler rollers in the upper run and in the lower run, a subframe (1) for lifting the web belt (7) and for holding the web belt (7), such that a sufficient clearance is formed for replacing worn-out idler rollers (53) by means of a changing frame (2). A service vehicle is equipped with a lifting apparatus for moving dividing devices. The process steps include lifting the web belt (7), removing the old idler roller (53old), inserting the new idler roller (53new) and lowering the web belt (7). The drawing shows the use of two dividing devices in the replacing of idler rollers in the upper run.