The invention provides a radioactive ray fluoroscopy device, radioactive ray fluoroscopy can be carried out from three or more positions without the need of moving a radioactive ray irradiation part and a radioactive ray detector. A control part (30) comprises a detection rate calculating part (32) which respectively calculates the detection rates of a first photography system, a second photography system, a third photography system and a fourth photography system for the position of a marker, wherein the first photography system comprises a first X-ray tube (11) and a first flat plate detector (21), the second photography system comprise a second X-ray tube (12) and a second flat plate detector (22), the third photography system comprises a third X-ray tube (13) and a third flat plate detector (23), and the fourth photography system comprises a fourth X-ray tube (14) and a fourth flat plate detector (24); a photography system selection part (33) selects two photography systems used for X-ray fluoroscopy from the first photography system, the second photography system, the third photography system and the fourth photography system based on the detection rate for the position of themarker which is calculated by the detection rate calculating part (32).