A search apparatus includes a storage device storing for particle data, positional information and a deformation gradient tensor; and a processor configured to generate based on the positional information, circumscribing shape data that circumscribes an influence region of the particle data; set, as a deformation object, the circumscribing shape data or region data; deform the deformation object by the deformation gradient tensor; judge whether an overlap exists between the deformed deformation object and a deformation-exempt object that is among the circumscribing shape data and the region data, and not set as the deformation object; determine particle data in the region data, as a neighbor particle data candidate of the object particle data, upon judging that an overlap exists between the deformed deformation object and the deformation-exempt object; and store to the storage device, a determination result.