1. A method of detecting space debris on a geocentric orbit, the space debris appearing on a plurality of images captured at time intervals during fixed point observation, the method comprising: an object identification step of identifying an object of breakup origin which is likely to have broken up on the geocentric orbit in the past; a virtual debris generation step of generating a virtual space debris piece in accordance with the law of conservation of mass by applying a debris breakup model to the object of breakup origin identified in the object identification step; an orbit calculation step of applying a debris orbit propagation model to each virtual space debris piece generated in the virtual debris generation step, thereby calculating an orbit of the virtual space debris piece during the fixed point observation; a motion vector distribution generation step of generating appearance frequency distribution of a motion vector of each virtual space debris piece on the celestial sphere during the fixed point observation on the basis of a result of the orbit calculation in the orbit calculation step; a motion vector estimation step of estimating the motion vector of the space debris piece on the images on the basis of a motion vector having a high level in the appearance frequency distribution on the basis of cumulative distribution of a plurality of appearance frequency distribution results of the motion vector obtained by performing the virtual debris generation step, the orbit calculation step, and the motion vector distribution generation step a plurality of times; and a detection step of cross-checking pieces of pixel information on respective regions in the images captured at time intervals during the fixed point observation, the regions shifted in a direction and in an amount of the estimated motion vector sequentially in the order of capture, thereby detecting space debris on the geocentric orbit appearing on the images.