Synthetic aperture radar signal processing device and synthetic aperture radar signal processing program

There are provided: a high-accuracy factor calculator for calculating, by a high-accuracy computation method, a distance R from a moving platform to a pixel position (a, b) within an observation target corresponding to an predicted position (xt, yt) and a phase factor A when a determination processor determines that an error is out of an allowable range; and a low-accuracy factor calculator for calculating, by a computation method with lower accuracy than that of the high-accuracy factor calculator (e.g., a computation method using an approximation algorithm), a distance R′ from the moving platform to the pixel position (a, b) corresponding to the predicted position (xt, yt) within the observation target and a phase factor A′ when the determination processor determines that the error is within the allowable range.