A method for detecting a residual crosslinking aid in a crosslinked resin molded body includes a subject heating step in which a crosslinked resin molded body is heated at a temperature of 500° C. or higher and 700° C. or lower for a time of 3 seconds or more and 30 seconds or less, a subject analysis step in which gas chromatographic analysis is performed on a gas generated in the subject heating step, and a detection step in which an unreacted crosslinking aid is detected on the basis of a peak originating from a residual crosslinking aid in a chromatogram obtained in the subject analysis step.