To provide an effective method of speedily, simple, and inexpensively pretreating an analysis sample for the analysis of dioxins while maintaining a high recovery rate with satisfactory reproducibility, and to provide a pretreating column for analyzing dioxins for implementing the method.

A diatomaceous earth column 10 having a silica gel layer 14, a sulfuric diatomaceous earth layer 16, and a polarity carrier layer 18 is connected to an active carbon column 20. By making a sample to be analyzed and a solvent flow down through the diatomaceous earth column 10 and making impurities adsorbed in the diatomaceous earth column 10, the dioxins are eluted into the active carbon column 20. The active carbon column 20 is inverted to make the solvent flow down to elute the dioxins.