The invention relates to the technical field of detecting devices and provides a radioactive source detecting and positioning device. The device comprises a moving unit, a pan/tilt head, a controllerand a gamma detector. The gamma detector comprises a casing, a scintillator, a photomultiplier and a shielding medium filled in the casing; an incoming hole is formed at the bottom end of the casing;a through hole is axially formed in the shielding medium in a penetration way; the photomultiplier and the scintillator are sequentially arranged in the top end of the through hole from top to bottom;the bottom end communicates with the incoming hole; the photomultiplier is electrically connected with the controller; the side wall of the casing is rotationally connected with the side wall of thepan/tilt head; and the pan/tilt head is arranged on the moving unit. According to the radioactive source detecting and positioning device in the invention, the shielding medium is filled in the casingof the gamma detector so that only the rays entering from the incoming hole are not weakened; and then, a to-be-detected space can be subjected to omnidirectional search through horizontal movement and rotation of the gamma detector, thereby determining the location of the radioactive source according to the magnitude of an electrical signal acquired by the controller.