This electromagnetic wave detector is provided with light reception graphene and reference graphene that are aligned on an insulating layer, first electrodes and second electrodes that are disposed so as to oppose each other and sandwich the light reception graphene and reference graphene, a gate electrode for applying a gate voltage to the light reception graphene and reference graphene, and a balanced circuit and detection circuit that are connected between the second electrodes. If electromagnetic waves are incident on the light reception graphene, photocarriers will be generated through in-band transition. If electromagnetic waves are incident on the reference graphene, photocarriers will not be generated because of the Pauli blocking effect. In a state where no electromagnetic waves are incident on the light reception graphene or reference graphene, the balanced circuit causes the first electrodes and second electrodes to have the same potential. The electrical signal between the second electrodes is detected in a state where electromagnetic waves are incident on the light reception graphene and reference graphene.