A rotational positioning mechanism includes a base, a rotational shaft, a rotational plate, at least two first switches and a positioning assembly. The rotational shaft is pivoted to the base. The rotational plate is connected to the rotational shaft and is configured to rotate relative to the base along with the rotational shaft. The rotational plate has at least two first positioning portions. The two first switches are respectively disposed at the two first positioning portions. The positioning assembly is disposed at the base. The positioning assembly comprises a positioning component configured to form a structural interference with anyone of the first positioning portions or remove the structural interference. After the positioning component forms the structural interference with anyone of the first positioning portions, the positioning component abuts against the corresponding first switch, and rotational degree of freedom of the rotational plate and the rotational shaft are restricted. A carrier is also provided.一種旋轉定位機構包括載座、轉軸、轉盤、至少二第一開關以及定位組件。轉軸樞設於載座。轉盤連接轉軸，且配置用以隨轉軸相對於載座旋轉。轉盤具有至少二第一定位部。前述二個第一開關分別設置於前述二個第一定位部。定位組件設置於載座。定位組件包括定位件，配置用以與任一個第一定位部產生結構干涉或解除結構干涉。在定位件與任一個第一定位部產生結構干涉後，定位件抵接對應的第一開關，且轉盤與轉軸的旋轉自由度被限制。另提出一種載具。
