A device (4A, 4B) for measuring a wheelset of railway vehicles, in particular for measuring geometric and / or dynamic parameters of a wheelset of passing railway vehicles, is shown and described, comprising: an inner longitudinal frame element (5i) for arrangement inside the rails (1A, 1B) approximately parallel to the rails (1A, 1B), an outer longitudinal frame element (5a) for arrangement outside the rails (1A, 1B) approximately parallel to the rails (1A, 1B), two transverse frame elements (6.1, 6.2) for arrangement below the rails (1A, 1B) approximately transverse to the rails (1A, 1B), and fastening elements (13a, 13i) for connecting a measuring frame (8A, 8B, 8') formed by the longitudinal frame elements (5a, 5i) and the transverse frame elements (6.1, 6.2) to the rail (1A, 1B). It is proposed that the inner longitudinal frame element (5i), the outer longitudinal frame element (5a) and the transverse frame elements (6.1, 6.2) are connected to each other by connecting elements (7) to form the measuring frame (8A, 8B, 8') and that at least two of the connecting elements (7) are designed as detachable connecting elements (7), in particular as detachable clamping elements, so that the measuring frame (8A, 8B, 8') can be disassembled into at least two parts.