An apparatus easily movable inside pipes for cutting off projections in the interior of the pipe along the inner surface of the pipe. The apparatus includes a carrier movable inside the pipe. The carrier is provided with a shaft reciprocatingly movable axially of the pipe and rockingly rotatable circumferentially of the pipe, a rocking block movable with the shaft and a drive device for the shaft. The rocking block has a cutter blade reciprocatingly movable axially and radially of the pipe as projected forward from the block axially of the pipe, and drive devices for the blade.