Device, related to the means for radiation therapy of malignant and benign neoplasms and certain other diseases, comprise hollow probe 5, source 1 of neutral particle radiation in the form of X-ray or gamma quanta or neutrons, and means of shaping the particle beam of said radiation oriented by the longitudinal axis of the probe. Means of shaping the particle beam is executed in the form of collimator or lens 18 comprising aggregate of curved channels for radiation transmission with a total internal reflection. Said means may be located inside of the probe 5. On using the device, probe 5 is introduced into the body of patient 11, with its distal end 7 approaching pathological locus 13 or inserted directly into it.For exposure of pathological locus, use is made of radiation of the neutral particles source directly or secondary radiation excited in the target placed in the distal end of the probe or radiation dissipated with this target.Design of the device requires no evacuation of the probe and use of high voltage in the latter, is easily transformed by the probe replacement, in particular, to change its size, to change energy and directional pattern of radiation affecting the pathological locus. Making of the probe removable simplifies its sterilization.