The invention relates to a pipe adjusting device for a tunnel pipe rack conveying and erecting machine. The pipe adjusting device comprises an adjusting support frame; a two-way piston hydraulic cylinder is fixedly connected to the support frame; two piston rods of the two-way piston hydraulic cylinder are fixedly connected to a frame; the support frame is fixedly connected with a slide plate; theframe is provided with a guide plate in sliding fit with the slide plate; adjusting hydraulic cylinders are mounted on the two sides of the support frame; and an adjusting lifting belt is connected between the two adjusting hydraulic cylinders. The pipe adjusting device has the following advantages: when steel pipes are conveyed to a customized operation surface for butt joint with adjacent steelpipes, the steel pipes can be adjusted up and down and left and right by the conveying and erecting machine; and during butt joint of the steel pipes, the roundness of the joints is deviated, and thesteel pipes can be rotationally adjusted by any angle to meet the steel pipe lifting operation requirements under arc construction working conditions.