An oxygen concentration device is provided which, when the number of revolutions of a compressor reaches an upper limit of control, increases an oxygen concentration, and can extend an operating time of the oxygen concentration device, comprising a control means which controls the number of revolutions of the compressor based on a detected value of an oxygen concentration sensor, judges deterioration due to moisture absorption based on the detected value of the oxygen concentration sensor, a detected value of a pressure sensor, and an operating time of an adsorption cylinder and, when criteria for judgment of the deterioration due to moisture absorption are satisfied, makes a purge step time shorter than an initially set time.