A graphene optoelectronic detector is disclosed, which comprises: an insulating substrate with a graphene layer disposed thereon; a first electrode disposed on the graphene layer or between the graphene layer and the insulating substrate; and a second electrode disposed on the graphene layer or between the graphene layer and the insulating substrate, wherein there is a predetermined distance between the first electrode and the second electrode, and the first electrode and the second electrode are at different electrical potentials, wherein a high-drift carrier moving region is disposed between the first electrode and the second electrode, and a low-drift carrier moving region is disposed outside the high-drift carrier moving region. In addition, the present invention further provides a method for detecting photons and electromagnetic energy using the aforementioned graphene detector.