The invention discloses an inside diameter measurement device which comprises an inside diameter measurement mechanism, a drive mechanism, a fixing jig of a workpiece to be measured and a control module. The inside diameter measurement device comprises a movable measurement pin, two fixed measurement pines, a measurement driver and a displacement sensor. The measurement driver is used for drivingthe movable measurement pine so as to enable the movable measurement pin and the two fixed measurement pint to contact with the inner wall of a round hole to be measured. The displacement sensor is used for detecting the displacement of the movable measurement pin the measurement process of the inner diameter. The control module is connected with the displacement sensor and used for calculating the inner diameter of the round hole to the measured according to the displacement. The invention further discloses an inside diameter measurement method. The inside diameter measurement device and themeasurement method thereof can accurately measure the dimension of the inner diameter and can effectively avoid the occurrence of batch points.