A work measuring method for measuring a work including a columnar member and a diaphragm and held by a positioner includes an acquiring step of acquiring point cloud data on a surface of the work held by the positioner and photographed in a predetermined direction, a detecting step of identifying a portion where distribution of the point cloud data changes in a three-dimensional coordinate system of the positioner and detecting the portion as a boundary position between the columnar member and the diaphragm, and a deriving step of deriving the number of columnar members and diaphragms included in the work on the basis of the boundary position detected in the detecting step.