The present study attempted to investigate the effects of supply of highly concentrated (30%) oxygen on human ability of visuospatial cognition and cerebrum lateralization. compared to air of normal oxygen concentration (21%). The experiment consisted of two runs, one fur visuospatial cognition test with normal air (21% of oxygen) and for visuospatial cognition test with more oxygen in the air (30% of oxygen). Each run was composed of four blocks and each block included eight control tasks and five visuospatial tasks. Functional brain images were taken from 3T MRI using the single-shot EPI method. The result of task performance showed the accuracy increased at 30%＇s concentration of oxygen rather than 21%＇s. There were more activations observed at the left and right hemisphere, but there was decrease cerebrum lateralization with 30% oxygen administration. Thus, it is concluded that the positive effect on the visuospatial cognitive performance level by the highly concentrated oxygen administration was due to increase of cerebrum activation and decrease of cerebrum lateralization