In this study, electron microscopy, Fractography and Jic test have been used to investigate the fracture behaviour in the scope of aging temperature which 7075 Al-alloy can have high strength. Conclusions obtained on this study are as followed. 1) When the 7075 Al-alloy was aged for 24hrs at 120℃, it`s mechanical properties was excellent but fracture toughness decrement resulted from intergranular fracture was emerged. 2) The state of aged for 24hrs at 100℃, had the highest fracture toughess. 3) We could infer that intergranular fracture occurred because preferrential precpitated precipitates in the grain boundary growed in the form of colinear along the grain boundary.