An oxygen concentration apparatus comprising: pressure swing adsorption type oxygen concentration means including: at least one adsorption column formed of a cylinder hollow having first and second ports, an inside of said cylinder hollow is filled with an adsorbent for selectively adsorbing nitrogen rather than oxygen; pressurized air supply means connected with the first port of said adsorption column and arranged to supply pressurized air to said adsorption columr; exhaust means connected with the first port of said adsorption column and allowing exhaust from said adsorption column; and switching means for allowing said pressurized air supply means and said exhaust means to communicate with said first port selectively, said pressure swing adsorption type oxygen concentration means being arranged to generate oxygen concentrated gas by repeating an adsorption process, in which said pressurized air supply means supplies pressurized air to said adsorption column to adsorb the nitrogen from said air, and a regeneration process, in which said exhaust means depressurizes said adsorption karate the nitrogen adsorbed by said adsorption column to regenerate said adsorbent; a conduit communicating at its one end with the second port of said oxygen concentration means and arranged to introduce the oxygen concentrated gas generated by said oxygen concentration means from said second port into a user; flow rate adjusting means provided in said conduit and arranged to adjust a flow rate of the oxygen concentrated gas generated by said oxygen concentration means; pressure measuring means disposed between said oxygen concentration means and said flow rate adjusting means in said conduit; and control means for controlling at least the switching means of said oxygen concentration means and said flow rate adjusting means, wherein said control means is arranged to adjust a cycle of the adsorption and regeneration processes of said oxygen concentration means to control pressure is at the upstream of said flow rate adjusting means by controlling said switching means based on pressure of said oxygen concentrated gas in said conduit measured by said pressure measuring means. pressure swing adsorption type oxygen concentration means including: at least one adsorption column formed of a cylinder hollow having first and second ports, an inside of said cylinder hollow is filled with an adsorbent for selectively adsorbing nitrogen rather than oxygen; pressurized air supply means connected with the first port of said adsorption column and arranged to supply pressurized air to said adsorption columr; exhaust means connected with the first port of said adsorption column and allowing exhaust from said adsorption column; and switching means for allowing said pressurized air supply means and said exhaust means to communicate with said first port selectively, said pressure swing adsorption type oxygen concentration means being arranged to generate oxygen concentrated gas by repeating an adsorption process, in which said pressurized air supply means supplies pressurized air to said adsorption column to adsorb the nitrogen from said air, and a regeneration process, in which said exhaust means depressurizes said adsorption karate the nitrogen adsorbed by said adsorption column to regenerate said adsorbent; a conduit communicating at its one end with the second port of said oxygen concentration means and arranged to introduce the oxygen concentrated gas generated by said oxygen concentration means from said second port into a user; flow rate adjusting means provided in said conduit and arranged to adjust a flow rate of the oxygen concentrated gas generated by said oxygen concentration means; pressure measuring means disposed between said oxygen concentration means and said flow rate adjusting means in said conduit; and control means for controlling at least the switching means of said oxygen concentration means and said flow rate adjusting means, wherein said control means is arranged to adjust a cycle of the adsorption and regeneration processes of said oxygen concentration means to control pressure is at the upstream of said flow rate adjusting means by controlling said switching means based on pressure of said oxygen concentrated gas in said conduit measured by said pressure measuring means.