Abstract: An apparatus for inspecting a pipeline having a pig body which measures an inner shape and a wall thickness of a pipe body, travelling inside the pipe body, comprises: at least one distance measuring device for measuring a travelling distance of the pig body; a rotation angle gauge for measuring a rotation angle of the pig body round its center axis; a plurality of transducers for transmitting and receiving ultrasonic beams being arranged in the circumferential direction of the pig body and being confronted with the inner surface of the pipe body, which measures the inner shape and the wall thickness of the pipe body; a recorder of the pig body which stores measured data; a signal processing device for processing signals from the distance measuring device, the rotation angle gauge and the transducers; and a data processing device for analyzing the measured data stored in the recorder after the pig body has been taken out of the pipe body.