1. A nuclear medicine diagnosis apparatus comprising: a mechanical collimator having a plurality of through-holes for allowing passage of photons having a predetermined energy emitted from an object to be examined into which a drug containing radioactive isotope is injected or dosed, in a predetermined direction; a former-stage detector for detecting positional information at a point of reaction where the photons passing through the mechanical collimator are scattered and energy information on the momentum of charged particles generated by the reaction; a latter-stage detector disposed in a subsequent stage of the former-stage detector to detect energy information on the photons scattered by the former-stage detector; and image reconstruction means for reconstructing an image from detection information collected from the former-stage detector and the latter-stage detector, wherein the image reconstruction means is configured to differentiate more than three levels of the energy information on the photons passed through the mechanical collimator and the energy information on the photons scattered by the former-stage detector, and perform image reconstruction by different image reconstruction algorithms from individual levels of the differentiated more than three levels of energy information, and wherein the image reconstruction means differentiates the detection energy information into energy information on movement direction of photons passed through the mechanical collimator, energy information on the direction of photons simultaneously detected by the respective detection means, and energy information on direction of photons scattered by Compton scattering.