Measuring device and measuring method

The invention provides a measuring device which can easily determine the wearing state of a rope wheel without dismounting a cover. A measurement device for measuring a gap between a main rope and a groove in a sheave, the sheave having a groove around which the main rope is wound and a cover having a gap through which the main rope passes, the measurement device driving the main rope by winding the main rope around the groove and rotating the main rope, the measurement device being provided with: a main body that comes into contact with the main rope; a gauge portion extending in a predetermined direction and insertable into a gap larger than a gap between the main cord and the groove when the groove reaches a wear limit; and a passage section that can be inserted into the gap between themain cord and the cover integrally with the main body, has a length that reaches the gap between the main cord and the groove when the measurement device is provided at the measurement position, andhas a passage through whic