Door mechanism capable of sliding and pivoting and electronic device therewith

A door mechanism includes a cover, a connecting bracket, a rotary door, a sliding bracket and a sliding button. The sliding button is connected to the sliding bracket. As the sliding button slides to a stopping position relative to the sliding bracket, the sliding button contacts against the rotary door for constraining the rotary door from moving in a first direction and the sliding button drives the sliding bracket to a position where the sliding bracket is stopped for constraining the rotary door from pivoting relative to the cover. As the sliding button slides to an unlocking position, the sliding button drives the sliding bracket to a position where the sliding bracket is not stopped and the rotary door can move in the first direction so that the rotary door can pivot relative to the cover so as to expose a containing space of a housing.