A signal processing device including: a detecting mechanism that, based upon a predetermined stable state, outputs a shake signal corresponding to shake of a device body from the stable state; a DC removing mechanism that outputs a DC component removing signal obtained by removing a predetermined low frequency component from the shake signal of said detecting mechanism; a calculating mechanism that calculates attenuation characteristics of the shake signal attenuated in said DC removing mechanism; and a generating mechanism that generates a composite signal obtained by combining said DC component removing signal with an attenuating signal corresponding to the attenuation characteristics calculated in said calculating mechanism, as the shake signal representing shake of the device body.