Roundness error measurement instrument for large bearings

The utility model relates to a roundness error measurement instrument for large bearings, which consists of a dial indicator, fulcrums, bolts, nuts, an annular reinforcing band, a first support, a second support, a third support and a fourth support, wherein the first support, the second support, the third support, the fourth support and the annular band are welded together, and the fulcrums and the dial indicator are fixed on the supports by the bolts and the nuts. During the measurement, the fulcrums are fixed on the first support and the third support, the dial indicator is fixed on the fourth support, or the fulcrums are fixed on the second support and the third support, and the dial indicator is fixed on the fourth support. The utility model has the following advantages: the utility model can accurately measure the roundness errors of medium and large bearings, the structure is simple, and the use is convenient.