As augmented reality (AR) with depth is popularized rapidly, it is important to clarify the effect of visual attention to information presented in different depth for a safe AR. Previous study using object substitution masking (OSM) showed that depth differences strongly affected to attention under binocular viewing. However, there is also another type of AR where information is presented in one eye. Using OSM, we investigated the visibility of information presented in different depth under monocular environment. The results suggested that the visibility was lower under monocular-AR than binocular-AR because attention would be obstructed by the lack of convergence-divergence eye-movements and/or parallax.