Although the water-cement ratio of concrete for the prestressed concrete is low, deterioration due to salt attack of prestressed concrete structures has appeared in recent years. Blast-furnace slag is effective in resisting penetration of chloride ions. However, the influences of blast-furnace slag on the durability properties of high-strength concrete for steam-cured pretensioned elements are not clear. In this study, carbonation and chloride penetration of the high-strength concrete using blast-furnace slag were examined. As the result, the addition of blast-furnace slag increased the concentration of chloride ion near the surface, but decreased the penetration to the interior concrete. Blast-furnace slag improved the resistance to erosion by a calcium chloride solution. Moreover, it was found that carbonation of the concrete made with blast-furnace slag was slow and there was no problem in this respect.