A vehicle periphery monitoring system, comprising a left side blind spot camera, imaging a front left side area from the vehicle which is in a blind spot for a driver of the vehicle; a right side blind spot camera, imaging a front right side area from the vehicle which is in a blind spot for the driver of the vehicle; a monitor set at a position in a vehicle interior to be viewed by the driver; and a monitor display image data generating means generating one of left and right monitor display image data based on right and left side real camera images which are input from the right side blind spot camera and the left side blind spot camera, respectively, wherein the monitor display image data generating means is configured - to divide the left side real camera image into two of a left vehicle body image part including a left tire image and the other left periphery image part, - to divide the right side real camera image into two of a right vehicle body image part including a right tire image and the other right periphery image part, - to set a point which is obtained by converting the driver's viewpoint in a line-symmetrical manner with a center axis of the vehicle as a line-symmetrical axis as an assistant driver's viewpoint, - to perform a viewpoint conversion of one of the left or right periphery image parts (L2, R2) into a conversion image (Ma2, Ga2) to be viewed from the driver's viewpoint, - to perform a viewpoint conversion of the other one of the left or right vehicle body image parts (R1, L1) into a semitransparent conversion image (Gb1, Mb1) to be viewed from the assistant driver's viewpoint and then performs a mirror image conversion of the semitransparent conversion image (Gb1, Mb1) into a semitransparent mirrored conversion image (Gb3, Mb3), - and to perform an image composition, superimposing the semitransparent mirrored conversion image (Gb3, Mb3) on the conversion image (Ma2, Ga2) to generate one of the left and right monitor display image data. - to divide the left side real camera image into two of a left vehicle body image part including a left tire image and the other left periphery image part, - to divide the right side real camera image into two of a right vehicle body image part including a right tire image and the other right periphery image part, - to set a point which is obtained by converting the driver's viewpoint in a line-symmetrical manner with a center axis of the vehicle as a line-symmetrical axis as an assistant driver's viewpoint, - to perform a viewpoint conversion of one of the left or right periphery image parts (L2, R2) into a conversion image (Ma2, Ga2) to be viewed from the driver's viewpoint, - to perform a viewpoint conversion of the other one of the left or right vehicle body image parts (R1, L1) into a semitransparent conversion image (Gb1, Mb1) to be viewed from the assistant driver's viewpoint and then performs a mirror image conversion of the semitransparent conversion image (Gb1, Mb1) into a semitransparent mirrored conversion image (Gb3, Mb3), - and to perform an image composition, superimposing the semitransparent mirrored conversion image (Gb3, Mb3) on the conversion image (Ma2, Ga2) to generate one of the left and right monitor display image data.