The present invention provides a novel treatment of alopecia areate. The problem to be solved by the invention is to provide a new pharmaceutical use of 3-[(3S,4R)-3-methyl-6-(7H-pyrrolo[2,3-d] pyrimidin-4-yl)-1,6-diazaspiro[3.4]octan-1-yl]-3-oxopropanenitrile. A therapeutic or preventive agent for alopecia areata, containing 3-[(3S,4R)-3-methyl-6-(7H-pyrrolo[2,3-d]pyrimidin-4-yl)-1,6-diazaspiro-[3.4]octan-1-yl]-3-oxopropanenitrile as an active ingredient.本發明提供圓禿之新穎治療。 本發明解決之問題係提供3-[(3S,4R)-3-甲基-6-(7H-吡咯并[2,3-d]嘧啶-4-基)-1,6-二氮雜螺[3.4]辛-1-基]-3-側氧基丙腈之新穎醫藥用途。本發明係關於用於圓禿之治療性或預防性藥劑,其含有3-[(3S,4R)-3-甲基-6-(7H-吡咯并[2,3-d]嘧啶-4-基)-1,6-二氮雜螺[3.4]辛-1-基]-3-側氧基丙腈作為活性成份。