To make a user easily obtain an objective and stable analysis result of bone mineral density. An analyzer 100 of bone mineral density using CT image data of a phantom having a known bone mineral density includes: a known data storage part 105 that stores known data of bone mineral density for a phantom; a histogram production part 102 that produces a histogram of region number relative to a CT value for three-dimensional CT image data of the phantom; a correspondence determination part 106 that determines correspondence between a CT value and a bone mineral density by correlating CT values showing respective peaks of the produced histogram with the known data of the phantom; and an analysis part 109 that decides a bone mineral density for three-dimensional CT image data of a subject using the determined correspondence.