Possible influence of d.c. magnetic fields on the behavior of oxygen dissolved in aqueous solutions is studied in order to widen the basic understanding of biological effects of magnetic fields. Oxygen concentration in the solution is controlled either by introduction of oxygen gas into the solution until the solution is saturated with oxygen gas at 1 atm pure oxygen, or by introduction of argon gas into the solution until the solution is saturated with argon gas it 1 atm pure argon. Then, the solution is contacted with air at 1 atm pressure. During the recovery process of the dissolved oxygen concentration from the nonequilibrium state to the equilibrium state, a part of the solution is exposed to 1.0 T magnetic field with a gradient of 10 T/m for 30 - 60 min. The spatial distribution of oxygen concentration in the solution was redistributed by the magnetic field. The relative change in oxygen concentration with position was around ±1 - ±7 %. In contrast, in the experiment under the equilibrium state of oxygen pressure, no redistribution of the dissolved oxygen was observed.