A device for detecting moisture for use with a device for monitoring an access to a patient for an extracorporeal blood treatment apparatus is described. The device for detecting moisture is constituted as a two-dimensionally extending fabric to be placed on the patient's skin, having an electrically conductive structure as a moisture sensor and constituted by non-conductive and conductive warp and weft threads configured to produce in the woven fabric a defined electrically conductive structure through spatial separation of the warp and weft threads. By the use of conductive warp and weft threads, an electrically conductive structure can be constituted having sections running in different directions, thereby creating a moisture sensor exhibiting a particularly high degree of sensitivity. The electrically conductive structure is preferably terminated with a terminating resistor, preferably not a component part but rather part of a connection part of the device, so that production is simplified.