The invention relates to a device for the optional guiding of at least one self-steering wheel of a trolley. According to the invention, the wheel is of the type that is mounted on a support that pivots around a vertical axis. The device comprises: a push bar which forms a dual-articulated steering member that can be accessed by the user; means for rotating a first clutch part about the vertical axis in response to steering member movements; and means which can be used at will to couple and uncouple the first clutch part in relation to a second clutch part which is solidly connected to the aforementioned support of the wheel, in response to other steering member movements. In addition, a coin-operated locking device for preventing the movement of the trolley is built into a casing which houses a transmission element of the guiding device and which is fixed to the push bar of the trolley.