The invention relates to a two-piece ostomy device comprising a base plate for adhering to the skin surrounding a stoma and a releasable collecting bag for collecting output from said stoma. The base plate is releasably connectable to the collecting bag via a first annular flange arranged on the base plate and a second annular flange arranged on the collecting bag. An adhesive is at least partly disposed on at least one of the flanges. The ostomy device further comprises a first through-going hole extending through the first annular flange along a first axis and a second through-going hole extending through the second annular flange along a second axis, wherein the ostomy device further comprises a guiding aid for arranging the first annular flange and the second annular flange in a guiding configuration. In the guiding configuration the movement of the first and the second flange is limited relative to each other in one plane being defined by the first and the second axis and in rotation around at least one of the first or the second axis. The limited movement of the base plate and the collecting bag provides a two-piece system which is easier to apply correctly and thus reduces the risk of leakage.
