Abstract: To propose an oral cavity sensor capable of analyzing tongue movements in more detail than before. In an oral cavity sensor (1) which is even provided with a sensor element (7) having a mechanical configuration capable of measuring each of external force components in three axis directions, the sensor element (7) can be protected by an elastic body (9), and the whole of the elastic body (9) is covered with the coating film (11a) made of a biocompatible material. Thereby, the sensor element (7) and the elastic body (9) can be safely attached in an oral cavity (MT) of a subject (EXA), and can measure each of the external force components in the three axis directions. As a result, on the basis of the external force components in the three axis directions, complicated tongue movements at the time of mastication or swallowing in the oral cavity (MT) can be analyzed in more detail than before.