An electromagnetic wave detection apparatus (10) includes an irradiator (11), a first detector (17), a memory (19), and a controller (20). The irradiator (11) irradiates electromagnetic waves. The first detector (17) includes detection elements. The detection elements detect, by irradiation position, reflected waves of the electromagnetic waves irradiated on an object (ob). The memory (19) stores first related information including an emission direction of the emitted electromagnetic waves. The controller (20) updates the first related information based on the position of the detection element, among the detection elements, that detects the reflected waves of the electromagnetic waves.