To provide an earthquake damage estimating device and its program for simply performing high-accuracy estimation on the state of a damage to a building caused by an earthquake.

A CPU 22 thereinto inputs, through a keyboard 14, etc., construction position information signifying the construction position of a building which is an estimating object on an earthquake damage and building kind information signifying the kind of the building. The CPU 22 acquires: response spectrum information signifying an acceleration response spectrum as to an earthquake motion of a ground surface corresponding to the assortment of ground in the construction position signified by the position information; and performance information signifying earthquake resisting performance corresponding to the kind of the building signified by the kind information. The CPU 22 generates adapted seismic-wave information by adapting reference seismic-wave information to the response spectrum, with the seismic-wave information signifying a reference seismic wave serving as a reference of a seismic wave used for earthquake damage estimation and the response spectrum being signified by the spectrum information. Based on the performance information and the seismic-wave information, the CPU 22 prepares earthquake damage estimation information making it possible to estimate the state of damage to the building caused by the earthquake motion which is an estimating object of earthquake damage to display the estimation information by means of a display 18.