To obtain a dioxin-degrading microorganism excellent in degrading and removing efficiency of dioxin, to provide a method for degrading the dioxin and to obtain a new waste culture medium suitable for use in the method for degrading the dioxin.

This microorganism is Pleurotus ostreatus 1 or Pleurotus ostreatus 2 belonging to the genus Pleurotus of the family Pleurotaceae or Pycnoporus coccineus 1 belonging to the genus Pycnoporus of the family Polyporaceae. The microorganism having the ability to degrade the dioxin and belonging to the genus Pleurotus of the family Pleurotaceae or the microorganism having the ability to degrade the dioxin and belonging to the genus Pycnoporus of the family Polyporaceae is used in the method for degrading the dioxin. The waste culture medium comprises the microorganism having the ability to degrade the dioxin and belonging to the genus Pleurotus of the family Pleurotaceae or the microorganism having the ability to degrade the dioxin and belonging to the genus Pycnoporus of the family Polyporaceae.