PROBLEM TO BE SOLVED: To improve the image quality of a generated image by supplementing an open space between scanning positions without increasing operation time even if open space are generated between scanning positions.SOLUTION: An observation device 1 includes a light scanning part 5 for making illumination light L scan an observation target, a light detecting element 8 for detecting return light L returning from each scanning position in the observation target in designated sampling period by emitting illumination light by means of the light scanning part, and an image generation part 9 for generating an image for the observation target by arranging the image drawing block including pixels more than one having the intensity of the return right from each scanning position detected by that light detecting element in the positional relationship corresponding to each scanning position. The image generation part sets the size of the image drawing block so that it overlaps the image drawing block which is adjoin each other.
