Concentration of tritium in highly tritiated water was measured by exposing imaging plates (IPs) to water vapor. Tritium penetrated into photostimulated luminescence (PSL) phosphor through polyethylene terephthalate protection layer, and well detectable signal of PSL was induced at tritium concentration of 16 kBq cm-3. In addition, tritium was reversibly desorbed by keeping IPs in air, and signal from IPs returned to background level. In other words, IPs exposed to tritiated water vapor were reusable; tritium concentration in water could be measured without any waste. In addition, no handling of tritiated water such as sampling and dilution was necessary.