To provide a method and a device capable of measuring, with high accuracy in a short time, a pitch or fall of a blade group arranged in parallel, such as a blade group of reeds used for a loom.

This device is equipped with a holding stand for holding the parallel blade group, a sensor carrier moving relatively in the blade arrangement direction (the weft insertion direction in the case of the reeds) of the parallel blade group held on the holding stand, two pairs of floodlights for projecting a first laser beam 8 and a second laser beam 9 from the front to the back of the parallel blade group, and a light receiver. The floodlights and the light receiver are loaded on the sensor carrier, and the first laser beam and the second laser beam are projected at different angles relative to an axis in the blade arrangement direction of the parallel blade group. The first and second laser beams are projected toward the blades, and simultaneously the sensor carrier is scanned in the blade arrangement direction.