1. A living body observation system comprising: an illuminating light generation section configured to generate first light with a peak wavelength in a blue region and second light with a peak wavelength in a red region; an image pickup section configured to pick up an image of return light from an object illuminated by the light emitted from the illuminating light generation section; a computation section configured to calculate a difference degree that is a value indicating a degree of difference between a luminance value of a first image obtained by picking up an image of return light of the first light and a luminance value of a second image obtained by picking up an image of return light of the second light in a same pixel; an enhancement processing section configured to execute a process of increasing a luminance value of a pixel in which the difference degree exceeds a predetermined threshold among respective pixels included in the first image in order to enhance a contrast of the pixel in which the difference degree exceeds the predetermined threshold relative to a pixel in which the difference degree calculated by the computation section does not exceed the predetermined threshold; and an observation image creation section configured to create an observation image by using the first image after the process by the enhancement processing section and the second image and output the created observation image to a display apparatus.