Apparatus and method for inspecting pipeline are provided. The pipeline inspecting apparatus moving along an external circumferential surface of a pipeline to inspect the pipeline, includes: a main frame having an arc shape having an opened portion to surround the pipeline; a main movement unit that is movably installed on the main frame, wherein the main movement unit is movably installed along a length direction of the pipeline while being in contact with the external circumferential surface of the pipeline; an auxiliary frame that has an arc shape having an opened portion to surround the pipeline and is separated from the main frame to face the main frame; an auxiliary frame adjusting unit that movably connects the auxiliary frame to the main movement unit in a circumferential direction of the pipeline; and a sensor adjusting unit that is fixed to the auxiliary frame, wherein a sensor for inspecting a state of the pipeline is installed.