Polymeric composites can be subjected to a wide variety of environmemtal conditions in practical use. One of most important conditions to be considered in the stuctural design using such materials is the miisture envirnment. Thus the moisture effect on interlaminar fracture toughness $G_IC$ and $G_IIC$ of CFRP(carbon fiber reinforced plastic) composed of carbon fibers and epoxy resin is studied in this paper. Specimens were first processed in 25, 50, $80^{circ}C$ flesh water and $25^{circ}C$ sea water for various periods of time. After that, the water absorption and fracture toughness tests were performed under laboratory atmosphere. As result, the specimen processed in $80^{circ}C$ flesh water indicates the highest misture absorbing capability, the second in $50^{circ}C$ flesh water, the third in $25^{circ}C$ sea water, and the specimen in $25^{circ}C$ flesh water does the lowest. The interlaminar fracture toughness $G_IC$ increases, approaches to the maximum, and decreases as the immersion time increases. In case of interlaminar $G_IIC$, the value of the specimen processed in $80^{circ}C$ flesh water turns out to be higher than others. In addition, the scanning electron micrographs(SEM) of fracture surfaces were also examined in order to explain the mechanism of fracture.