To provide an image forming device capable of easily and surely printing a paper sheet in a desirable color.

This image forming device detects color of the paper sheets respectively housed in a plurality of paper feeding cassettes (paper sheet housing sections) housing paper sheets to be supplied to an image forming section for forming an image (step S2), and selects a paper feeding cassette to be used to supply the paper sheet to the image forming section among the plurality of paper feeding cassettes (step S3).