Looks like a plain pleated miniskirt to me, except a bit shorter than usual. I love winry's design, its so simple, but still really nice looking.
FB cosplay page https://www.facebook.com/Moonandstarcosplay
cosplays im working on: Tifa Lockhart(FF7) Ruby Rose(RWBY), Kirito GGO Version and Mother's Rosario Kirito(SAO) Kuroyukihime school avatar (Accel World) Rin Tohsaka (Fate/Stay Night)
Cosplays ive done: Sephiroth(FF7), Kirito SAO and ALO versions, Kazuto Kirigaya casual outfit and school uniform(SAO), Homura Akemi(PMMM), Namine(KH), and Kuroyukihime school uniform (Accel World)