An oxygen enriching apparatus which can supply oxygen or oxygen-enriched gas to a user at proper timings, as well as a controller and recording medium therefore. In step 100, a signal from a pressure sensor 53 is input. In subsequent step 110, on the basis of the signal output from the pressure sensor 53, a judgment is made as to whether the state of inhalation can be detected. When the result of judgment is “Yes,” this means that an anomalous state exists. In this case, the processing proceeds to step 120. When the result of judgment is “No,” this means that the patient and the apparatus are normal. In this case, the present processing is suspended. When start of inhalation cannot be detected over, for example, a period of 10 seconds or more, an anomalous state is judged to have arisen. In step 120, because of the anomalous state having arisen, the electromagnetic valve 47 is driven to open the supply passage 29 so as to supply oxygen-enriched gas over a period of about 4 seconds. Subsequently, the present processing is suspended.