A method and a device for diagnosis and state monitoring of a wear and functional state of a junction, a crossing, a crossroads, rail joints, and/or track nonuniformities of a rail traffic path made of several tracks measures and stores swing acceleration in at least one direction when overtaking a rail vehicle on a junction, crossings or crossroads, in addition to rail joints or track nonuniformities on at least one rail vehicle component, the swing acceleration being produced on the rail vehicle component when overtaking the rail vehicle at the junction, crossing or crossroads, rail joints, track nonuniformites. The method also measures and stores the rail vehicle speed and determines and stores the travel direction and the place of the junction, crossing or crossroads, rail joints, track nonuniformities, carries out a control as to whether characteristic, predetermined threshold values of the measured swing accelerations have been exceeded.