A synthetic aperture radar signal processing device, comprising: a low-accuracy interpolation processing unit configured to perform coordinate transformation by performing interpolation processing on discrete data that is obtained by performing an azimuth compression on signals received by a synthetic aperture radar; a high-accuracy interpolation processing unit configured to perform coordinate transformation by performing interpolation processing on the discrete data with higher accuracy than the low-accuracy interpolation processing unit; a curvature determination unit configured to select interpolation processing of either the high-accuracy interpolation processing unit or the low-accuracy interpolation processing unit in accordance with a first curvature that is a curvature of the discrete data at a target area for the interpolation processing; and an image reproduction processing unit configured to reproduce an image by use of a result of the interpolation processing selected by the curvature determination unit, wherein the curvature determination unit is configured to: select a point A, a point B, and a point C of discrete data adjacently arranged in a predetermined direction near a target area for the interpolation processing; determine, as a curvature of the discrete data at the target area, a first curvature based on a distance Δf 1R between the point C and a point externally dividing a line segment connecting the point A and the point B at (AB+BC):BC, where AB is a distance between the point A and the point B, and BC is a distance between the point B and the point C. a low-accuracy interpolation processing unit configured to perform coordinate transformation by performing interpolation processing on discrete data that is obtained by performing an azimuth compression on signals received by a synthetic aperture radar; a high-accuracy interpolation processing unit configured to perform coordinate transformation by performing interpolation processing on the discrete data with higher accuracy than the low-accuracy interpolation processing unit; a curvature determination unit configured to select interpolation processing of either the high-accuracy interpolation processing unit or the low-accuracy interpolation processing unit in accordance with a first curvature that is a curvature of the discrete data at a target area for the interpolation processing; and an image reproduction processing unit configured to reproduce an image by use of a result of the interpolation processing selected by the curvature determination unit, wherein the curvature determination unit is configured to: select a point A, a point B, and a point C of discrete data adjacently arranged in a predetermined direction near a target area for the interpolation processing; determine, as a curvature of the discrete data at the target area, a first curvature based on a distance Δf 1R between the point C and a point externally dividing a line segment connecting the point A and the point B at (AB+BC):BC, where AB is a distance between the point A and the point B, and BC is a distance between the point B and the point C. select a point A, a point B, and a point C of discrete data adjacently arranged in a predetermined direction near a target area for the interpolation processing; determine, as a curvature of the discrete data at the target area, a first curvature based on a distance Δf 1R between the point C and a point externally dividing a line segment connecting the point A and the point B at (AB+BC):BC, where AB is a distance between the point A and the point B, and BC is a distance between the point B and the point C.