[Problems] To provide a novel active clay having superior decolorizing performance to the conventional active clays and a decolorizing agent comprising the active clay for animal and plant fats and oils or for mineral oils.[Means for Solution] The active clay has a porous volume of 0.40 to 0.60 cm3/g with porous sizes of 1.7 to 100 nm as measured by the nitrogen adsorption method, a porous volume ratio (B/A) of the porous volume (A) with porous sizes of 1.7 to 11.5 nm and the porous volume (B) with porous sizes of not smaller than 11.5 nm but not larger than 100 nm in a range of 0.75 to 1.5, and an amount of solid acid of Ho≦−3.0 in a range of 0.15 to 0.40 mmols/g.