A method is provided that can form a clear textural structure image of a processed food or a raw material for the processed. Also, said method can form an image clear enough to clearly discern even an intertwined structure of starches, proteins and lipids of a processed food or a raw material for the processed food. The method includes light-exciting the processed food or the raw material for the processed food which is stained with a fluorescent dye having triphenylmethane skeleton; collecting data about the light-excited processed food or the light-excited raw material using at least three kinds of monitoring lights, that is, a monitoring light A having a fluorescence wavelength of 380 nm or longer and shorter than 450 nm, a monitoring light B having a fluorescence wavelength of 450 nm or longer and shorter than 560 nm, and a monitoring light C having a fluorescence wavelength of 560 nm to 700 nm; and forming an image on the basis of the collected data.