Inner diameter detection device

The utility model belongs to the technical field of mechanical equipment detection, and particularly relates to an inner diameter detection device which comprises a first placing part, a first scale sticker is fixedly adhered to the front surface of the first placing part, a second placing part is fixedly arranged on one side, close to the first scale sticker, of the front surface of the first placing part, and the second placing part is of a hollow structure. A circuit board is fixedly arranged in the second placing part, and a single chip microcomputer is fixedly arranged on the outer surface of the circuit board; an electric push rod and a single chip microcomputer are in signal connection through a controller, a worker places an abutting plate on the inner wall of a gun barrel, a first placing part is fixed through the abutting plate, a connecting part and a mounting part, then the electric push rod is controlled to stretch out and draw back, and a first patch is attached to the inner wall of the gun barr