As a method for using a hard X-ray sensor that can detect weak hard X-rays or the like with a higher resolution, a method for accurately evaluating natural resources of crude oil, natural gas, etc. existing underground, for example, is provided. A buried object evaluating method includes a detecting step of arranging a radiation detector to be opposed to a hard X-ray source radiating first hard X-rays with a buried object buried in a first substance being interposed between the radiation detector and the radiation source and, by using the radiation detector, detecting second hard X-rays transmitted through the buried object out of the first hard X-rays and third hard X-rays not transmitted through the buried object, and an evaluating step of evaluating the buried object based on a strength of the first hard X-rays and a strength of the second hard X-rays detected by the radiation detector.