A boron neutron capture therapy system provided with a neutron beam irradiation device inside a room covered with neutron beam shielding, and configured to perform treatment by irradiating neutron beams onto an affected part, into which boron compounds have been injected, of a patient, using the neutron beam irradiation device, the boron neutron capture therapy system comprising: a plurality of cameras configured to capture images of the patient; a patient restraint/placement portion configured to restrain the patient in a state of being placed on the patient restraint/placement portion; a three-dimensional diagnostic device configured to detect a position of the affected part in the patient; an irradiation table whose position is determined with respect to the neutron beam irradiation device; a position adjustment mechanism configured to change a position of the irradiation table with respect to an irradiation port of the neutron beam irradiation device, in relation to each of directions of three axes that are mutually orthogonal; and a control unit configured to align a position of the affected part in the patient detected by the three-dimensional diagnostic device with a position of neutron beams irradiated from the neutron beam irradiation device by changing, using the position adjustment mechanism, a position relating to each of the directions of the three axes of the irradiation table onto which the patient restraint/placement portion has been transferred, and configured to move the affected part as close as possible to the irradiation port, wherein the control unit is configured to three-dimensionally measure a shape of a contour of the body of the patient restrained on the patient restraint/placement portion using images from the plurality of cameras, to estimate a spatial position of the contour of the body according to the movement of the irradiation table prior to movement of the irradiation table by simulation, and to perform collision avoidance processing that changes the movement of the irradiation table before the patient restrained on the patient restraint/placement portion receives injury by colliding with the irradiation port. a plurality of cameras configured to capture images of the patient; a patient restraint/placement portion configured to restrain the patient in a state of being placed on the patient restraint/placement portion; a three-dimensional diagnostic device configured to detect a position of the affected part in the patient; an irradiation table whose position is determined with respect to the neutron beam irradiation device; a position adjustment mechanism configured to change a position of the irradiation table with respect to an irradiation port of the neutron beam irradiation device, in relation to each of directions of three axes that are mutually orthogonal; and a control unit configured to align a position of the affected part in the patient detected by the three-dimensional diagnostic device with a position of neutron beams irradiated from the neutron beam irradiation device by changing, using the position adjustment mechanism, a position relating to each of the directions of the three axes of the irradiation table onto which the patient restraint/placement portion has been transferred, and configured to move the affected part as close as possible to the irradiation port, wherein the control unit is configured to three-dimensionally measure a shape of a contour of the body of the patient restrained on the patient restraint/placement portion using images from the plurality of cameras, to estimate a spatial position of the contour of the body according to the movement of the irradiation table prior to movement of the irradiation table by simulation, and to perform collision avoidance processing that changes the movement of the irradiation table before the patient restrained on the patient restraint/placement portion receives injury by colliding with the irradiation port.