In an apparatus on a spinning preparation machine, for example, a flat card, roller card, draw frame or the like, for monitoring fiber material, having at least one rotating roller that delivers fiber material, and a monitoring arrangement device that detects undesirable accumulations (build-up) of fiber material and emits an electrical signal is present. To permit immediate detection of undesirable accumulations of material in a structurally simple manner, the monitoring arrangement comprises a non-contact sensor arrangement (sensor), which is capable of detecting undesirable accumulations of fiber material.