The present invention pertains to a device for ultrasonic inspection of a weld seam of a longitudinally welded pipe for longitudinal defects with an inspection unit, which is relatively displaceable on a pipe surface on at least one side of the weld seam. The device also has two inspection heads in a tandem and spatially-variable arrangement, such that they can be positioned relative to the pipe surface to correspond to an intended acoustic irradiation angle independent of the diameter of the pipe. According to the invention, one inspection head acts as a transmitter and the other inspection head acts as a receiver. The device also has a pick-up connected to each of the two inspection heads, a coupling means connection connected to each pick-up, and a replaceable connecting element connected each pick-up via the coupling means connection.