An imaging device and method which can easily obtain a curve of time-varying changes in pixel value of a region of interest, even if the region of interest moves with a subject's body motion. A controller includes an image processor executing various types of image processing on fluorescence images and visible light images. The image processor includes a pixel value measurement unit which sequentially measures values of pixels at positions corresponding to a region of interest (ROI) in the fluorescence image, a change curve creation unit which creates a curve of time-varying changes in pixel value of the ROI by sampling, among the pixel values measured by the pixel value measurement unit, a minimum pixel value within a period equal to or longer than a cycle of the subject's body motion, and a smoothing unit which smooths the curve created by the change curve creation unit.
